diff --git a/include/net/iptfs.h b/include/net/iptfs.h
new file mode 100644
index 000000000000..d8f2e494f251
--- /dev/null
+++ b/include/net/iptfs.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NET_IPTFS_H
+#define _NET_IPTFS_H
+
+#include <linux/types.h>
+#include <linux/ip.h>
+
+#define IPTFS_SUBTYPE_BASIC 0
+#define IPTFS_SUBTYPE_CC 1
+#define IPTFS_SUBTYPE_LAST IPTFS_SUBTYPE_CC
+
+#define IPTFS_CC_FLAGS_ECN_CE 0x1
+#define IPTFS_CC_FLAGS_PLMTUD 0x2
+
+extern void xfrm_iptfs_get_rtt_and_delays(struct ip_iptfs_cc_hdr *cch, u32 *rtt,
+					  u32 *actual_delay, u32 *xmit_delay);
+
+#endif /* _NET_IPTFS_H */
diff --git a/net/xfrm/Makefile b/net/xfrm/Makefile
index cd47f88921f5..9b870a3274a7 100644
--- a/net/xfrm/Makefile
+++ b/net/xfrm/Makefile
@@ -20,4 +20,5 @@ obj-$(CONFIG_XFRM_USER) += xfrm_user.o
 obj-$(CONFIG_XFRM_USER_COMPAT) += xfrm_compat.o
 obj-$(CONFIG_XFRM_IPCOMP) += xfrm_ipcomp.o
 obj-$(CONFIG_XFRM_INTERFACE) += xfrm_interface.o
+obj-$(CONFIG_XFRM_IPTFS) += xfrm_iptfs.o
 obj-$(CONFIG_XFRM_ESPINTCP) += espintcp.o
diff --git a/net/xfrm/trace_iptfs.h b/net/xfrm/trace_iptfs.h
new file mode 100644
index 000000000000..994b6dafd1ef
--- /dev/null
+++ b/net/xfrm/trace_iptfs.h
@@ -0,0 +1,224 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* xfrm_trace_iptfs.h
+ *
+ * August 12 2023, Christian Hopps <chopps@labn.net>
+ *
+ * Copyright (c) 2023, LabN Consulting, L.L.C.
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM iptfs
+
+#if !defined(_TRACE_IPTFS_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_IPTFS_H
+
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/tracepoint.h>
+#include <net/ip.h>
+
+struct xfrm_iptfs_data;
+
+TRACE_EVENT(iptfs_egress_recv,
+	    TP_PROTO(struct sk_buff *skb, struct xfrm_iptfs_data *xtfs, u16 blkoff),
+	    TP_ARGS(skb, xtfs, blkoff),
+	    TP_STRUCT__entry(
+		    __field(struct sk_buff *, skb)
+		    __field(void *, head)
+		    __field(void *, head_pg_addr)
+		    __field(void *, pg0addr)
+		    __field(u32, skb_len)
+		    __field(u32, data_len)
+		    __field(u32, headroom)
+		    __field(u32, tailroom)
+		    __field(u32, tail)
+		    __field(u32, end)
+		    __field(u32, pg0off)
+		    __field(u8, head_frag)
+		    __field(u8, frag_list)
+		    __field(u8, nr_frags)
+		    __field(u16, blkoff)),
+	    TP_fast_assign(
+		    __entry->skb = skb;
+		    __entry->head = skb->head;
+		    __entry->skb_len = skb->len;
+		    __entry->data_len = skb->data_len;
+		    __entry->headroom = skb_headroom(skb);
+		    __entry->tailroom = skb_tailroom(skb);
+		    __entry->tail = skb->tail;
+		    __entry->end = skb->end;
+		    __entry->head_frag = skb->head_frag;
+		    __entry->frag_list = (bool)skb_shinfo(skb)->frag_list;
+		    __entry->nr_frags = skb_shinfo(skb)->nr_frags;
+		    __entry->blkoff = blkoff;
+		    __entry->head_pg_addr = page_address(virt_to_head_page(skb->head));
+		    __entry->pg0addr = (__entry->nr_frags
+					? page_address(skb_shinfo(skb)->frags[0].bv_page)
+					: 0);
+		    __entry->pg0off = (__entry->nr_frags ? skb_shinfo(skb)->frags[0].bv_offset : 0);
+
+		    ),
+	    TP_printk("EGRESS: skb=%p len=%u data_len=%u headroom=%u head_frag=%u frag_list=%u nr_frags=%u blkoff=%u\n\t\ttailroom=%u tail=%u end=%u head=%p hdpgaddr=%p pg0->addr=%p pg0->data=%p pg0->off=%u",
+		      __entry->skb, __entry->skb_len, __entry->data_len, __entry->headroom,
+		      __entry->head_frag, __entry->frag_list, __entry->nr_frags, __entry->blkoff,
+		      __entry->tailroom, __entry->tail, __entry->end, __entry->head,
+		      __entry->head_pg_addr, __entry->pg0addr, __entry->pg0addr + __entry->pg0off,
+		      __entry->pg0off)
+	)
+
+DECLARE_EVENT_CLASS(iptfs_ingress_preq_event,
+		    TP_PROTO(struct sk_buff *skb, struct xfrm_iptfs_data *xtfs,
+			     u32 pmtu, u8 was_gso),
+		    TP_ARGS(skb, xtfs, pmtu, was_gso),
+		    TP_STRUCT__entry(
+			__field(struct sk_buff *, skb)
+			__field(u32, skb_len)
+			__field(u32, data_len)
+			__field(u32, pmtu)
+			__field(u32, queue_size)
+			__field(u32, proto_seq)
+			__field(u8, proto)
+			__field(u8, was_gso)
+			    ),
+		    TP_fast_assign(
+			    __entry->skb = skb;
+			    __entry->skb_len = skb->len;
+			    __entry->data_len = skb->data_len;
+			    __entry->queue_size = xtfs->cfg.max_queue_size - xtfs->queue_size;
+			    __entry->proto = __trace_ip_proto(ip_hdr(skb));
+			    __entry->proto_seq = __trace_ip_proto_seq(ip_hdr(skb));
+			    __entry->pmtu = pmtu;
+			__entry->was_gso = was_gso;
+			    ),
+		    TP_printk("INGRPREQ: skb=%p len=%u data_len=%u qsize=%u proto=%u proto_seq=%u pmtu=%u was_gso=%u",
+			      __entry->skb, __entry->skb_len, __entry->data_len,
+			      __entry->queue_size, __entry->proto, __entry->proto_seq,
+			      __entry->pmtu, __entry->was_gso));
+
+DEFINE_EVENT(iptfs_ingress_preq_event, iptfs_enqueue,
+	     TP_PROTO(struct sk_buff *skb, struct xfrm_iptfs_data *xtfs, u32 pmtu, u8 was_gso),
+	     TP_ARGS(skb, xtfs, pmtu, was_gso));
+
+DEFINE_EVENT(iptfs_ingress_preq_event, iptfs_no_queue_space,
+	     TP_PROTO(struct sk_buff *skb, struct xfrm_iptfs_data *xtfs, u32 pmtu, u8 was_gso),
+	     TP_ARGS(skb, xtfs, pmtu, was_gso));
+
+DEFINE_EVENT(iptfs_ingress_preq_event, iptfs_too_big,
+	     TP_PROTO(struct sk_buff *skb, struct xfrm_iptfs_data *xtfs, u32 pmtu, u8 was_gso),
+	     TP_ARGS(skb, xtfs, pmtu, was_gso));
+
+DECLARE_EVENT_CLASS(
+	iptfs_ingress_postq_event,
+	TP_PROTO(struct sk_buff *skb, u32 mtu, u16 blkoff, struct iphdr *iph),
+	TP_ARGS(skb, mtu, blkoff, iph),
+	TP_STRUCT__entry(__field(struct sk_buff *, skb)
+			 __field(u32, skb_len)
+			 __field(u32, data_len)
+			 __field(u32, mtu)
+			 __field(u32, proto_seq)
+			 __field(u16, blkoff)
+			 __field(u8, proto)),
+	TP_fast_assign(__entry->skb = skb;
+		       __entry->skb_len = skb->len;
+		       __entry->data_len = skb->data_len;
+		       __entry->mtu = mtu;
+		       __entry->blkoff = blkoff;
+		       __entry->proto = iph ? __trace_ip_proto(iph) : 0;
+		       __entry->proto_seq = iph ? __trace_ip_proto_seq(iph) : 0;
+		),
+	TP_printk(
+		"INGRPSTQ: skb=%p len=%u data_len=%u mtu=%u blkoff=%u proto=%u proto_seq=%u",
+		__entry->skb, __entry->skb_len, __entry->data_len, __entry->mtu,
+		__entry->blkoff, __entry->proto, __entry->proto_seq));
+
+DEFINE_EVENT(iptfs_ingress_postq_event, iptfs_first_dequeue,
+	     TP_PROTO(struct sk_buff *skb, u32 mtu, u16 blkoff,
+		      struct iphdr *iph),
+	     TP_ARGS(skb, mtu, blkoff, iph));
+
+DEFINE_EVENT(iptfs_ingress_postq_event, iptfs_first_fragmenting,
+	     TP_PROTO(struct sk_buff *skb, u32 mtu, u16 blkoff,
+		      struct iphdr *iph),
+	     TP_ARGS(skb, mtu, blkoff, iph));
+
+DEFINE_EVENT(iptfs_ingress_postq_event, iptfs_first_final_fragment,
+	     TP_PROTO(struct sk_buff *skb, u32 mtu, u16 blkoff,
+		      struct iphdr *iph),
+	     TP_ARGS(skb, mtu, blkoff, iph));
+
+DEFINE_EVENT(iptfs_ingress_postq_event, iptfs_first_toobig,
+	     TP_PROTO(struct sk_buff *skb, u32 mtu, u16 blkoff,
+		      struct iphdr *iph),
+	     TP_ARGS(skb, mtu, blkoff, iph));
+
+TRACE_EVENT(iptfs_ingress_nth_peek,
+	    TP_PROTO(struct sk_buff *skb, u32 remaining),
+	    TP_ARGS(skb, remaining),
+	    TP_STRUCT__entry(__field(struct sk_buff *, skb)
+			     __field(u32, skb_len)
+			     __field(u32, remaining)),
+	    TP_fast_assign(__entry->skb = skb;
+			   __entry->skb_len = skb->len;
+			   __entry->remaining = remaining;
+		    ),
+	    TP_printk("INGRPSTQ: NTHPEEK: skb=%p len=%u remaining=%u",
+		      __entry->skb, __entry->skb_len, __entry->remaining));
+
+TRACE_EVENT(iptfs_ingress_nth_add, TP_PROTO(struct sk_buff *skb, u8 share_ok),
+	    TP_ARGS(skb, share_ok),
+	    TP_STRUCT__entry(__field(struct sk_buff *, skb)
+			     __field(u32, skb_len)
+			     __field(u32, data_len)
+			     __field(u8, share_ok)
+			     __field(u8, head_frag)
+			     __field(u8, pp_recycle)
+			     __field(u8, cloned)
+			     __field(u8, shared)
+			     __field(u8, nr_frags)
+			     __field(u8, frag_list)
+		    ),
+	    TP_fast_assign(__entry->skb = skb;
+			   __entry->skb_len = skb->len;
+			   __entry->data_len = skb->data_len;
+			   __entry->share_ok = share_ok;
+			   __entry->head_frag = skb->head_frag;
+			   __entry->pp_recycle = skb->pp_recycle;
+			   __entry->cloned = skb_cloned(skb);
+			   __entry->shared = skb_shared(skb);
+			   __entry->nr_frags = skb_shinfo(skb)->nr_frags;
+			   __entry->frag_list = (bool)skb_shinfo(skb)->frag_list;
+		    ),
+	    TP_printk("INGRPSTQ: NTHADD: skb=%p len=%u data_len=%u share_ok=%u head_frag=%u pp_recycle=%u cloned=%u shared=%u nr_frags=%u frag_list=%u",
+		      __entry->skb, __entry->skb_len, __entry->data_len, __entry->share_ok,
+		      __entry->head_frag, __entry->pp_recycle, __entry->cloned, __entry->shared,
+		      __entry->nr_frags, __entry->frag_list));
+
+DECLARE_EVENT_CLASS(iptfs_timer_event,
+		    TP_PROTO(struct xfrm_iptfs_data *xtfs, u64 time_val),
+		    TP_ARGS(xtfs, time_val),
+		    TP_STRUCT__entry(
+			__field(u64, time_val)
+			__field(u64, set_time)),
+		    TP_fast_assign(
+			__entry->time_val = time_val;
+			__entry->set_time = xtfs->iptfs_settime;
+		    ),
+		    TP_printk("TIMER: set_time=%llu time_val=%llu",
+			      __entry->set_time, __entry->time_val));
+
+DEFINE_EVENT(iptfs_timer_event, iptfs_timer_start,
+	     TP_PROTO(struct xfrm_iptfs_data *xtfs, u64 time_val),
+	     TP_ARGS(xtfs, time_val));
+
+DEFINE_EVENT(iptfs_timer_event, iptfs_timer_expire,
+	     TP_PROTO(struct xfrm_iptfs_data *xtfs, u64 time_val),
+	     TP_ARGS(xtfs, time_val));
+
+#endif /* _TRACE_IPTFS_H */
+
+/* This part must be outside protection */
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH ../../net/xfrm
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace_iptfs
+#include <trace/define_trace.h>
diff --git a/net/xfrm/xfrm_iptfs.c b/net/xfrm/xfrm_iptfs.c
new file mode 100644
index 000000000000..65f7acdbe6a8
--- /dev/null
+++ b/net/xfrm/xfrm_iptfs.c
@@ -0,0 +1,2696 @@
+// SPDX-License-Identifier: GPL-2.0
+/* xfrm_iptfs: IPTFS encapsulation support
+ *
+ * April 21 2022, Christian Hopps <chopps@labn.net>
+ *
+ * Copyright (c) 2022, LabN Consulting, L.L.C.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/icmpv6.h>
+#include <net/gro.h>
+#include <net/icmp.h>
+#include <net/ip6_route.h>
+#include <net/inet_ecn.h>
+#include <net/iptfs.h>
+#include <net/xfrm.h>
+
+#include <crypto/aead.h>
+
+#include "xfrm_inout.h"
+#include "trace_iptfs.h"
+
+/* 1) skb->head should be cache aligned.
+ * 2) when resv is for L2 headers (i.e., ethernet) we want the cacheline to
+ * start -16 from data.
+ * 3) when resv is for L3+L2 headers IOW skb->data points at the IPTFS payload
+ * we want data to be cache line aligned so all the pushed headers will be in
+ * another cacheline.
+ */
+#define XFRM_IPTFS_MIN_L3HEADROOM 128
+#define XFRM_IPTFS_MIN_L2HEADROOM (64 + 16)
+#define IPTFS_FRAG_COPY_MAX 256	/* max for copying to create iptfs frags */
+#define IPTFS_PKT_SHARE_MIN 129	/* min to try to share vs copy pkt data */
+#define NSECS_IN_USEC 1000
+
+#define IPTFS_TYPE_NOCC 0
+#define IPTFS_TYPE_CC 1
+
+#define IPTFS_HRTIMER_MODE HRTIMER_MODE_REL_SOFT
+
+struct skb_wseq {
+	struct sk_buff *skb;
+	u64 drop_time;
+};
+
+struct xfrm_iptfs_config {
+	bool dont_frag : 1;
+	u16 reorder_win_size;
+	u32 pkt_size;	    /* outer_packet_size or 0 */
+	u32 max_queue_size; /* octets */
+	u64 init_delay_us;  /* microseconds */
+	u32 drop_time_us;   /* microseconds */
+};
+
+struct xfrm_iptfs_data {
+	struct xfrm_iptfs_config cfg;
+
+	/* Ingress User Input */
+	struct xfrm_state *x;	    /* owning state */
+	struct sk_buff_head queue;  /* output queue */
+	u32 queue_size;		    /* octets */
+	u32 ecn_queue_size;	    /* octets above which ECN mark */
+	u64 init_delay_ns;	    /* nanoseconds */
+	struct hrtimer iptfs_timer; /* output timer */
+	time64_t iptfs_settime;	    /* time timer was set */
+	u32 payload_mtu;	    /* max payload size */
+
+	/* Tunnel input reordering */
+	bool w_seq_set;		  /* true after first seq received */
+	u64 w_wantseq;		  /* expected next sequence */
+	struct skb_wseq *w_saved; /* the saved buf array */
+	u32 w_savedlen;		  /* the saved len (not size) */
+	spinlock_t drop_lock;
+	struct hrtimer drop_timer;
+	u64 drop_time_ns;
+
+	/* Tunnel input reassembly */
+	struct sk_buff *ra_newskb; /* new pkt being reassembled */
+	u64 ra_wantseq;		   /* expected next sequence */
+	u8 ra_runt[6];		   /* last pkt bytes from last skb */
+	u8 ra_runtlen;		   /* count of ra_runt */
+};
+
+static u32 __iptfs_get_inner_mtu(struct xfrm_state *x, int outer_mtu);
+static enum hrtimer_restart iptfs_delay_timer(struct hrtimer *me);
+static enum hrtimer_restart iptfs_drop_timer(struct hrtimer *me);
+
+/* ================= */
+/* Utility Functions */
+/* ================= */
+
+static u32 __trace_ip_proto(struct iphdr *iph)
+{
+	if (iph->version == 4)
+		return iph->protocol;
+	return ((struct ipv6hdr *)iph)->nexthdr;
+}
+
+static u32 __trace_ip_proto_seq(struct iphdr *iph)
+{
+	void *nexthdr;
+	u32 protocol = 0;
+
+	if (iph->version == 4) {
+		nexthdr = (void *)(iph + 1);
+		protocol = iph->protocol;
+	} else if (iph->version == 6) {
+		nexthdr = (void *)(((struct ipv6hdr *)(iph)) + 1);
+		protocol = ((struct ipv6hdr *)(iph))->nexthdr;
+	}
+	switch (protocol) {
+	case IPPROTO_ICMP:
+		return ntohs(((struct icmphdr *)nexthdr)->un.echo.sequence);
+	case IPPROTO_ICMPV6:
+		return ntohs(((struct icmp6hdr *)nexthdr)->icmp6_sequence);
+	case IPPROTO_TCP:
+		return ntohl(((struct tcphdr *)nexthdr)->seq);
+	case IPPROTO_UDP:
+		return ntohs(((struct udphdr *)nexthdr)->source);
+	default:
+		return 0;
+	}
+}
+
+static u64 __esp_seq(struct sk_buff *skb)
+{
+	u64 seq = ntohl(XFRM_SKB_CB(skb)->seq.input.low);
+
+	return seq | (u64)ntohl(XFRM_SKB_CB(skb)->seq.input.hi) << 32;
+}
+
+/* ================= */
+/* SK_BUFF Functions */
+/* ================= */
+
+/**
+ * iptfs_alloc_skb() - Allocate a new `skb` using a meta-data template.
+ * @tpl: the template to copy the new `skb`s meta-data from.
+ * @len: the linear length of the head data, zero is fine.
+ * @l3resv: true if reserve needs to support pushing L3 headers
+ *
+ * A new `skb` is allocated and it's meta-data is initialized from `tpl`, the
+ * head data is sized to `len` + reserved space set according to the @l3resv
+ * boolean. When @l3resv is false, resv is XFRM_IPTFS_MIN_L2HEADROOM which
+ * arranges for `skb->data - 16` (etherhdr space) to be the start of a cacheline.
+ * Otherwise, @l3resv is true and resv is either the size of headroom from `tpl` or
+ * XFRM_IPTFS_MIN_L3HEADROOM whichever is greater, which tries to align
+ * skb->data to a cacheline as all headers will be pushed on the previous
+ * cacheline bytes.
+ *
+ * When copying meta-data from the @tpl, the sk_buff->headers are not copied.
+ *
+ * Zero length skbs are allocated when we only need a head skb to hold new
+ * packet headers (basically the mac header) that sit on top of existing shared
+ * packet data.
+ *
+ * Return: the new skb or NULL.
+ */
+static struct sk_buff *iptfs_alloc_skb(struct sk_buff *tpl, u32 len,
+				       bool l3resv)
+{
+	struct sk_buff *skb;
+	u32 resv;
+
+	if (!l3resv) {
+		resv = XFRM_IPTFS_MIN_L2HEADROOM;
+	} else {
+		resv = skb_headroom(tpl);
+		if (resv < XFRM_IPTFS_MIN_L3HEADROOM)
+			resv = XFRM_IPTFS_MIN_L3HEADROOM;
+	}
+
+	skb = alloc_skb(len + resv, GFP_ATOMIC);
+	if (!skb) {
+		XFRM_INC_STATS(dev_net(tpl->dev), LINUX_MIB_XFRMINERROR);
+		return NULL;
+	}
+
+	skb_reserve(skb, resv);
+
+	/* Code from __copy_skb_header() -- we do not want any of the
+	 * tpl->headers copied over, so we aren't using `skb_copy_header()`.
+	 */
+	skb->tstamp = tpl->tstamp;
+	skb->dev = tpl->dev;
+	memcpy(skb->cb, tpl->cb, sizeof(skb->cb));
+	skb_dst_copy(skb, tpl);
+	__skb_ext_copy(skb, tpl);
+	__nf_copy(skb, tpl, false);
+
+	return skb;
+}
+
+/**
+ * skb_head_to_frag() - initialize a skb_frag_t based on skb head data
+ */
+static void skb_head_to_frag(const struct sk_buff *skb, skb_frag_t *frag)
+{
+	struct page *page = virt_to_head_page(skb->data);
+	unsigned char *addr = (unsigned char *)page_address(page);
+
+	BUG_ON(!skb->head_frag);
+	skb_frag_fill_page_desc(frag, page, skb->data - addr, skb_headlen(skb));
+}
+
+/**
+ * struct skb_frag_walk - use to track a walk through fragments
+ * @fragi: current fragment index
+ * @past: length of data in fragments before @fragi
+ * @total: length of data in all fragments
+ * @nr_frags: number of fragments present in array
+ * @initial_offset: the value passed in to skb_prepare_frag_walk()
+ * @pp_recycle: copy of skb->pp_recycle
+ * @frags: the page fragments inc. room for head page
+ */
+struct skb_frag_walk {
+	u32 fragi;
+	u32 past;
+	u32 total;
+	u32 nr_frags;
+	u32 initial_offset;
+	bool pp_recycle;
+	skb_frag_t frags[MAX_SKB_FRAGS + 1];
+};
+
+/**
+ * skb_prepare_frag_walk() - initialize a frag walk over an skb.
+ * @skb: the skb to walk.
+ * @initial_offset: start the walk @initial_offset into the skb.
+ * @walk: the walk to initialize
+ *
+ * Future calls to skb_add_frags() will expect the @offset value to be at
+ * least @initial_offset large.
+ */
+static void skb_prepare_frag_walk(struct sk_buff *skb, u32 initial_offset,
+				  struct skb_frag_walk *walk)
+{
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	skb_frag_t *frag, *from;
+	u32 i;
+
+	walk->initial_offset = initial_offset;
+	walk->fragi = 0;
+	walk->past = 0;
+	walk->total = 0;
+	walk->nr_frags = 0;
+	walk->pp_recycle = skb->pp_recycle;
+
+	if (skb->head_frag) {
+		if (initial_offset >= skb_headlen(skb)) {
+			initial_offset -= skb_headlen(skb);
+		} else {
+			frag = &walk->frags[walk->nr_frags++];
+			skb_head_to_frag(skb, frag);
+			frag->bv_offset += initial_offset;
+			frag->bv_len -= initial_offset;
+			walk->total += frag->bv_len;
+			initial_offset = 0;
+		}
+	} else {
+		BUG_ON(skb_headlen(skb) > initial_offset);
+		initial_offset -= skb_headlen(skb);
+	}
+
+	for (i = 0; i < shinfo->nr_frags; i++) {
+		from = &shinfo->frags[i];
+		if (initial_offset >= from->bv_len) {
+			initial_offset -= from->bv_len;
+			continue;
+		}
+		frag = &walk->frags[walk->nr_frags++];
+		*frag = *from;
+		if (initial_offset) {
+			frag->bv_offset += initial_offset;
+			frag->bv_len -= initial_offset;
+			initial_offset = 0;
+		}
+		walk->total += frag->bv_len;
+	}
+	BUG_ON(initial_offset != 0);
+}
+
+static u32 __skb_reset_frag_walk(struct skb_frag_walk *walk, u32 offset)
+{
+	/* Adjust offset to refer to internal walk values */
+	BUG_ON(offset < walk->initial_offset);
+	offset -= walk->initial_offset;
+
+	/* Get to the correct fragment for offset */
+	while (offset < walk->past) {
+		walk->past -= walk->frags[--walk->fragi].bv_len;
+		if (offset >= walk->past)
+			break;
+		BUG_ON(walk->fragi == 0);
+	}
+	while (offset >= walk->past + walk->frags[walk->fragi].bv_len)
+		walk->past += walk->frags[walk->fragi++].bv_len;
+
+	/* offset now relative to this current frag */
+	offset -= walk->past;
+	return offset;
+}
+
+/**
+ * skb_can_add_frags() - check if ok to add frags from walk to skb
+ * @skb: skb to check for adding frags to
+ * @walk: the walk that will be used as source for frags.
+ * @offset: offset from beginning of original skb to start from.
+ * @len: amount of data to add frag references to in @skb.
+ */
+static bool skb_can_add_frags(const struct sk_buff *skb,
+			      struct skb_frag_walk *walk, u32 offset, u32 len)
+{
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	u32 fragi, nr_frags, fraglen;
+
+	if (skb_has_frag_list(skb) || skb->pp_recycle != walk->pp_recycle)
+		return false;
+
+	/* Make offset relative to current frag after setting that */
+	offset = __skb_reset_frag_walk(walk, offset);
+
+	/* Verify we have array space for the fragments we need to add */
+	fragi = walk->fragi;
+	nr_frags  = shinfo->nr_frags;
+	while (len && fragi < walk->nr_frags) {
+		skb_frag_t *frag = &walk->frags[fragi];
+
+		fraglen = frag->bv_len;
+		if (offset) {
+			fraglen -= offset;
+			offset = 0;
+		}
+		if (++nr_frags > MAX_SKB_FRAGS)
+			return false;
+		if (len <= fraglen)
+			return true;
+		len -= fraglen;
+		fragi++;
+	}
+	/* We may not copy all @len but what we have will fit. */
+	return true;
+}
+
+/**
+ * skb_add_frags() - add a range of fragment references into an skb
+ * @skb: skb to add references into
+ * @walk: the walk to add referenced fragments from.
+ * @offset: offset from beginning of original skb to start from.
+ * @len: amount of data to add frag references to in @skb.
+ *
+ * skb_can_add_frags() should be called before this function to verify that the
+ * destination @skb is compatible with the walk and has space in the array for
+ * the to be added frag refrences.
+ *
+ * Return: The number of bytes not added to @skb b/c we reached the end of the
+ * walk before adding all of @len.
+ */
+static int skb_add_frags(struct sk_buff *skb, struct skb_frag_walk *walk,
+			 u32 offset, u32 len)
+{
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	u32 fraglen;
+
+	BUG_ON(skb->pp_recycle != walk->pp_recycle);
+	if (!walk->nr_frags || offset >= walk->total + walk->initial_offset)
+		return len;
+
+	/* make offset relative to current frag after setting that */
+	offset = __skb_reset_frag_walk(walk, offset);
+	BUG_ON(shinfo->nr_frags >= MAX_SKB_FRAGS);
+
+	while (len && walk->fragi < walk->nr_frags) {
+		skb_frag_t *frag = &walk->frags[walk->fragi];
+		skb_frag_t *tofrag = &shinfo->frags[shinfo->nr_frags];
+
+		*tofrag = *frag;
+		if (offset) {
+			tofrag->bv_offset += offset;
+			tofrag->bv_len -= offset;
+			offset = 0;
+		}
+		__skb_frag_ref(tofrag);
+		shinfo->nr_frags++;
+		BUG_ON(shinfo->nr_frags > MAX_SKB_FRAGS);
+
+		/* see if we are done */
+		fraglen = tofrag->bv_len;
+		if (len < fraglen) {
+			tofrag->bv_len = len;
+			skb->len += len;
+			skb->data_len += len;
+			return 0;
+		}
+		/* advance to next source fragment */
+		len -= fraglen;		  /* careful, use dst bv_len */
+		skb->len += fraglen;	  /* careful, "   "    "     */
+		skb->data_len += fraglen; /* careful, "   "    "     */
+		walk->past +=
+			frag->bv_len; /* careful, use src bv_len */
+		walk->fragi++;
+	}
+	return len;
+}
+
+/**
+ * skb_copy_bits_seq - copy bits from a skb_seq_state to kernel buffer
+ * @st: source skb_seq_state
+ * @offset: offset in source
+ * @to: destination buffer
+ * @len: number of bytes to copy
+ *
+ * Copy @len bytes from @offset bytes into the source @st to the destination
+ * buffer @to. `offset` should increase (or be unchanged) with each subsequent
+ * call to this function. If offset needs to decrease from the previous use `st`
+ * should be reset first.
+ */
+static int skb_copy_bits_seq(struct skb_seq_state *st, int offset, void *to, int len)
+{
+	const u8 *data;
+	u32 sqlen;
+
+	for (;;) {
+		sqlen = skb_seq_read(offset, &data, st);
+		if (sqlen == 0)
+			return -ENOMEM;
+		if (sqlen >= len) {
+			memcpy(to, data, len);
+			return 0;
+		}
+		memcpy(to, data, sqlen);
+		to += sqlen;
+		offset += sqlen;
+		len -= sqlen;
+	}
+}
+
+/* ================================== */
+/* IPTFS Trace Event Definitions      */
+/* ================================== */
+
+#define CREATE_TRACE_POINTS
+#include "trace_iptfs.h"
+
+/* ================================== */
+/* IPTFS Receiving (egress) Functions */
+/* ================================== */
+
+/**
+ * iptfs_pskb_add_frags() - Create and add frags into a new sk_buff.
+ * @tpl: template to create new skb from.
+ * @walk: The source for fragments to add.
+ * @off: The offset into @walk to add frags from, also used with @st and
+ *       @copy_len.
+ * @len: The length of data to add covering frags from @walk into @skb.
+ *       This must be <= @skblen.
+ * @st: The sequence state to copy from into the new head skb.
+ * @copy_len: Copy @copy_len bytes from @st at offset @off into the new skb
+ *            linear space.
+ *
+ * Create a new sk_buff `skb` using the template @tpl. Copy @copy_len bytes from
+ * @st into the new skb linear space, and then add shared fragments from the
+ * frag walk for the remaining @len of data (i.e., @len - @copy_len bytes).
+ *
+ * Return: The newly allocated sk_buff `skb` or NULL if an error occurs.
+ */
+struct sk_buff *iptfs_pskb_add_frags(struct sk_buff *tpl,
+				     struct skb_frag_walk *walk, u32 off,
+				     u32 len, struct skb_seq_state *st,
+				     u32 copy_len)
+{
+	struct sk_buff *skb;
+
+	skb = iptfs_alloc_skb(tpl, copy_len, false);
+	if (!skb)
+		return NULL;
+
+	/* this should not normally be happening */
+	if (!skb_can_add_frags(skb, walk, off + copy_len, len - copy_len)) {
+		kfree_skb(skb);
+		return NULL;
+	}
+
+	if (copy_len &&
+	    skb_copy_bits_seq(st, off, skb_put(skb, copy_len), copy_len)) {
+		XFRM_INC_STATS(dev_net(st->root_skb->dev),
+			       LINUX_MIB_XFRMINERROR);
+		kfree_skb(skb);
+		return NULL;
+	}
+
+	skb_add_frags(skb, walk, off + copy_len, len - copy_len);
+	return skb;
+}
+
+/**
+ * iptfs_pskb_extract_seq() - Create and load data into a new sk_buff.
+ * @skblen: the total data size for `skb`.
+ * @st: The source for the rest of the data to copy into `skb`.
+ * @off: The offset into @st to copy data from.
+ * @len: The length of data to copy from @st into `skb`. This must be <=
+ *       @skblen.
+ *
+ * Create a new sk_buff `skb` with @skblen of packet data space. If non-zero,
+ * copy @rlen bytes of @runt into `skb`. Then using seq functions copy @len
+ * bytes from @st into `skb` starting from @off.
+ *
+ * It is an error for @len to be greater than the amount of data left in @st.
+ *
+ * Return: The newly allocated sk_buff `skb` or NULL if an error occurs.
+ */
+static struct sk_buff *
+iptfs_pskb_extract_seq(u32 skblen, struct skb_seq_state *st, u32 off, int len)
+{
+	struct sk_buff *skb = iptfs_alloc_skb(st->root_skb, skblen, false);
+
+	if (!skb)
+		return NULL;
+	if (skb_copy_bits_seq(st, off, skb_put(skb, len), len)) {
+		XFRM_INC_STATS(dev_net(st->root_skb->dev),
+			       LINUX_MIB_XFRMINERROR);
+		kfree_skb(skb);
+		return NULL;
+	}
+	return skb;
+}
+
+/**
+ * iptfs_input_save_runt() - save data in xtfs runt space.
+ *
+ * Save the small (`len`) start of a fragmented packet in `buf` in the xtfs data
+ * runt space.
+ */
+static void iptfs_input_save_runt(struct xfrm_iptfs_data *xtfs, u64 seq,
+				  u8 *buf, int len)
+{
+	BUG_ON(xtfs->ra_newskb); /* we won't have a new SKB yet */
+
+	memcpy(xtfs->ra_runt, buf, len);
+
+	xtfs->ra_runtlen = len;
+	xtfs->ra_wantseq = seq + 1;
+}
+
+/**
+ * __iptfs_iphlen() - return the v4/v6 header length using packet data.
+ *
+ * The version data is expected to be valid (i.e., either 4 or 6).
+ */
+static u32 __iptfs_iphlen(u8 *data)
+{
+	struct iphdr *iph = (struct iphdr *)data;
+
+	if (iph->version == 0x4)
+		return sizeof(*iph);
+	BUG_ON(iph->version != 0x6);
+	return sizeof(struct ipv6hdr);
+}
+
+/**
+ * __iptfs_iplen() - return the v4/v6 length using packet data.
+ *
+ * Grab the IPv4 or IPv6 length value in the start of the inner packet header
+ * pointed to by `data`. Assumes data len is enough for the length field only.
+ *
+ * The version data is expected to be valid (i.e., either 4 or 6).
+ */
+static u32 __iptfs_iplen(u8 *data)
+{
+	struct iphdr *iph = (struct iphdr *)data;
+
+	if (iph->version == 0x4)
+		return ntohs(iph->tot_len);
+	BUG_ON(iph->version != 0x6);
+	return ntohs(((struct ipv6hdr *)iph)->payload_len) +
+	       sizeof(struct ipv6hdr);
+}
+
+/**
+ * iptfs_complete_inner_skb() - finish preparing the inner packet for gro recv.
+ *
+ * Finish the standard xfrm processing on the inner packet prior to sending back
+ * through gro_cells_receive. We do this separately b/c we are building a list
+ * of packets in the hopes that one day a list will be taken by
+ * xfrm_input.
+ */
+static void iptfs_complete_inner_skb(struct xfrm_state *x, struct sk_buff *skb)
+{
+	skb_reset_network_header(skb);
+
+	/* The packet is going back through gro_cells_receive no need to
+	 * set this.
+	 */
+	skb_reset_transport_header(skb);
+
+	/* Packet already has checksum value set. */
+	skb->ip_summed = CHECKSUM_NONE;
+
+	/* Our skb will contain the header data copied when this outer packet
+	 * which contained the start of this inner packet. This is true
+	 * when we allocate a new skb as well as when we reuse the existing skb.
+	 */
+	if (ip_hdr(skb)->version == 0x4) {
+		struct iphdr *iph = ip_hdr(skb);
+
+		if (x->props.flags & XFRM_STATE_DECAP_DSCP)
+			ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, iph);
+		if (!(x->props.flags & XFRM_STATE_NOECN))
+			if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
+				IP_ECN_set_ce(iph);
+
+		skb->protocol = htons(ETH_P_IP);
+	} else {
+		struct ipv6hdr *iph = ipv6_hdr(skb);
+
+		if (x->props.flags & XFRM_STATE_DECAP_DSCP)
+			ipv6_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, iph);
+		if (!(x->props.flags & XFRM_STATE_NOECN))
+			if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
+				IP6_ECN_set_ce(skb, iph);
+
+		skb->protocol = htons(ETH_P_IPV6);
+	}
+}
+
+static void __iptfs_reassem_done(struct xfrm_iptfs_data *xtfs, bool free)
+{
+	int ret;
+
+	assert_spin_locked(&xtfs->drop_lock);
+
+	/* We don't care if it works locking takes care of things */
+	ret = hrtimer_try_to_cancel(&xtfs->drop_timer);
+	if (free)
+		kfree_skb(xtfs->ra_newskb);
+	xtfs->ra_newskb = NULL;
+}
+
+/**
+ * iptfs_reassem_done() - In-progress packet is aborted free the state.
+ */
+static void iptfs_reassem_abort(struct xfrm_iptfs_data *xtfs)
+{
+	__iptfs_reassem_done(xtfs, true);
+}
+
+/**
+ * iptfs_reassem_done() - In-progress packet is complete, clear the state.
+ */
+static void iptfs_reassem_done(struct xfrm_iptfs_data *xtfs)
+{
+	__iptfs_reassem_done(xtfs, false);
+}
+
+/**
+ * iptfs_reassem_cont() - Continue the reassembly of an inner packets.
+ *
+ * Process an IPTFS payload that has a non-zero `blkoff` or when we are
+ * expecting the continuation b/c we have a runt or in-progress packet.
+ */
+static u32 iptfs_reassem_cont(struct xfrm_iptfs_data *xtfs, u64 seq,
+			      struct skb_seq_state *st, struct sk_buff *skb,
+			      u32 data, u32 blkoff, struct list_head *list)
+{
+	struct skb_frag_walk _fragwalk;
+	struct skb_frag_walk *fragwalk = NULL;
+	struct sk_buff *newskb = xtfs->ra_newskb;
+	u32 remaining = skb->len - data;
+	u32 runtlen = xtfs->ra_runtlen;
+	u32 copylen, fraglen, ipremain, iphlen, iphremain, rrem;
+
+	/* Handle packet fragment we aren't expecting */
+	if (!runtlen && !xtfs->ra_newskb)
+		return data + min(blkoff, remaining);
+
+	/* Important to remember that input to this function is an ordered
+	 * packet stream (unless the user disabled the reorder window). Thus if
+	 * we are waiting for, and expecting the next packet so we can continue
+	 * assembly, a newer sequence number indicates older ones are not coming
+	 * (or if they do should be ignored). Technically we can receive older
+	 * ones when the reorder window is disabled; however, the user should
+	 * have disabled fragmentation in this case, and regardless we don't
+	 * deal with it.
+	 *
+	 * blkoff could be zero if the stream is messed up (or it's an all pad
+	 * insertion) be careful to handle that case in each of the below
+	 */
+
+	/* Too old case: This can happen when the reorder window is disabled so
+	 * ordering isn't actually guaranteed.
+	 */
+	if (seq < xtfs->ra_wantseq)
+		return data + remaining;
+
+	/* Too new case: We missed what we wanted cleanup. */
+	if (seq > xtfs->ra_wantseq) {
+		XFRM_INC_STATS(dev_net(skb->dev),
+			       LINUX_MIB_XFRMINIPTFSERROR);
+		goto abandon;
+	}
+
+	if (blkoff == 0) {
+		if ((*skb->data & 0xF0) != 0) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINIPTFSERROR);
+			goto abandon;
+		}
+		/* Handle all pad case, advance expected sequence number.
+		 * (RFC 9347 S2.2.3)
+		 */
+		xtfs->ra_wantseq++;
+		/* will end parsing */
+		return data + remaining;
+	}
+
+	if (runtlen) {
+		BUG_ON(xtfs->ra_newskb);
+
+		/* Regardless of what happens we're done with the runt */
+		xtfs->ra_runtlen = 0;
+
+		/* The start of this inner packet was at the very end of the last
+		 * iptfs payload which didn't include enough for the ip header
+		 * length field. We must have *at least* that now.
+		 */
+		rrem = sizeof(xtfs->ra_runt) - runtlen;
+		if (remaining < rrem || blkoff < rrem) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINIPTFSERROR);
+			goto abandon;
+		}
+
+		/* fill in the runt data */
+		if (skb_copy_bits_seq(st, data, &xtfs->ra_runt[runtlen],
+				      rrem)) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINBUFFERERROR);
+			goto abandon;
+		}
+
+		/* We have enough data to get the ip length value now,
+		 * allocate an in progress skb
+		 */
+		ipremain = __iptfs_iplen(xtfs->ra_runt);
+		if (ipremain < sizeof(xtfs->ra_runt)) {
+			/* length has to be at least runtsize large */
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINIPTFSERROR);
+			goto abandon;
+		}
+
+		/* For the runt case we don't attempt sharing currently. NOTE:
+		 * Currently, this IPTFS implementation will not create runts.
+		 */
+
+		newskb = iptfs_alloc_skb(skb, ipremain, false);
+		if (!newskb) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINERROR);
+			goto abandon;
+		}
+		xtfs->ra_newskb = newskb;
+
+		/* Copy the runt data into the buffer, but leave data
+		 * pointers the same as normal non-runt case. The extra `rrem`
+		 * recopied bytes are basically cacheline free. Allows using
+		 * same logic below to complete.
+		 */
+		memcpy(skb_put(newskb, runtlen), xtfs->ra_runt,
+		       sizeof(xtfs->ra_runt));
+	}
+
+	/* Continue reassembling the packet */
+	ipremain = __iptfs_iplen(newskb->data);
+	iphlen = __iptfs_iphlen(newskb->data);
+
+	/* Sanity check, we created the newskb knowing the IP length so the IP
+	 * length can't now be shorter.
+	 */
+	BUG_ON(newskb->len > ipremain);
+
+	ipremain -= newskb->len;
+	if (blkoff < ipremain) {
+		/* Corrupt data, we don't have enough to complete the packet */
+		XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMINIPTFSERROR);
+		goto abandon;
+	}
+
+	/* We want the IP header in linear space */
+	if (newskb->len < iphlen)  {
+		iphremain = iphlen - newskb->len;
+		if (blkoff < iphremain) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINIPTFSERROR);
+			goto abandon;
+		}
+		fraglen = min(blkoff, remaining);
+		copylen = min(fraglen, iphremain);
+		BUG_ON(skb_tailroom(newskb) < copylen);
+		if (skb_copy_bits_seq(st, data, skb_put(newskb, copylen), copylen)) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINBUFFERERROR);
+			goto abandon;
+		}
+		/* this is a silly condition that might occur anyway */
+		if (copylen < iphremain) {
+			xtfs->ra_wantseq++;
+			return data + fraglen;
+		}
+		/* update data and things derived from it */
+		data += copylen;
+		blkoff -= copylen;
+		remaining -= copylen;
+		ipremain -= copylen;
+	}
+
+	fraglen = min(blkoff, remaining);
+	copylen = min(fraglen, ipremain);
+
+	/* If we may have the opportunity to share prepare a fragwalk. */
+	if (!skb_has_frag_list(skb) && !skb_has_frag_list(newskb) &&
+	    (skb->head_frag || skb->len == skb->data_len) &&
+	    skb->pp_recycle == newskb->pp_recycle) {
+		fragwalk = &_fragwalk;
+		skb_prepare_frag_walk(skb, data, fragwalk);
+	}
+
+	/* Try share then copy. */
+	if (fragwalk && skb_can_add_frags(newskb, fragwalk, data, copylen)) {
+		u32 leftover;
+
+		leftover = skb_add_frags(newskb, fragwalk, data, copylen);
+		BUG_ON(leftover != 0);
+	} else {
+		/* We verified this was true in the main receive routine */
+		BUG_ON(skb_tailroom(newskb) < copylen);
+
+		/* copy fragment data into newskb */
+		if (skb_copy_bits_seq(st, data, skb_put(newskb, copylen), copylen)) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINBUFFERERROR);
+			goto abandon;
+		}
+	}
+
+	if (copylen < ipremain) {
+		xtfs->ra_wantseq++;
+	} else {
+		/* We are done with packet reassembly! */
+		BUG_ON(copylen != ipremain);
+		iptfs_reassem_done(xtfs);
+		iptfs_complete_inner_skb(xtfs->x, newskb);
+		list_add_tail(&newskb->list, list);
+	}
+
+	/* will continue on to new data block or end */
+	return data + fraglen;
+
+abandon:
+	if (xtfs->ra_newskb) {
+		iptfs_reassem_abort(xtfs);
+	} else {
+		xtfs->ra_runtlen = 0;
+		xtfs->ra_wantseq = 0;
+	}
+	/* skip past fragment, maybe to end */
+	return data + min(blkoff, remaining);
+}
+
+/**
+ * iptfs_input_ordered() - handle next in order IPTFS payload.
+ *
+ * Process the IPTFS payload in `skb` and consume it afterwards.
+ */
+static int iptfs_input_ordered(struct xfrm_state *x, struct sk_buff *skb)
+{
+	u8 hbytes[sizeof(struct ipv6hdr)];
+	struct ip_iptfs_cc_hdr iptcch;
+	struct skb_seq_state skbseq;
+	struct skb_frag_walk _fragwalk;
+	struct skb_frag_walk *fragwalk = NULL;
+	struct list_head sublist; /* rename this it's just a list */
+	struct sk_buff *first_skb, *defer, *next;
+	const unsigned char *old_mac;
+	struct xfrm_iptfs_data *xtfs;
+	struct ip_iptfs_hdr *ipth;
+	struct iphdr *iph;
+	struct net *net;
+	u32 remaining, first_iplen, iplen, iphlen, data, tail;
+	u32 blkoff, capturelen;
+	u64 seq;
+
+	xtfs = x->mode_data;
+	net = dev_net(skb->dev);
+	first_skb = NULL;
+	defer = NULL;
+
+	seq = __esp_seq(skb);
+
+	/* Large enough to hold both types of header */
+	ipth = (struct ip_iptfs_hdr *)&iptcch;
+
+	/* Save the old mac header if set */
+	old_mac = skb_mac_header_was_set(skb) ? skb_mac_header(skb) : NULL;
+
+	skb_prepare_seq_read(skb, 0, skb->len, &skbseq);
+
+	/* Get the IPTFS header and validate it */
+
+	if (skb_copy_bits_seq(&skbseq, 0, ipth, sizeof(*ipth))) {
+		XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);
+		goto done;
+	}
+	data = sizeof(*ipth);
+
+	trace_iptfs_egress_recv(skb, xtfs, htons(ipth->block_offset));
+
+	/* Set data past the basic header */
+	if (ipth->subtype == IPTFS_SUBTYPE_CC) {
+		/* Copy the rest of the CC header */
+		remaining = sizeof(iptcch) - sizeof(*ipth);
+		if (skb_copy_bits_seq(&skbseq, data, ipth + 1, remaining)) {
+			XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);
+			goto done;
+		}
+		data += remaining;
+	} else if (ipth->subtype != IPTFS_SUBTYPE_BASIC) {
+		XFRM_INC_STATS(net, LINUX_MIB_XFRMINHDRERROR);
+		goto done;
+	}
+
+	if (ipth->flags != 0) {
+		XFRM_INC_STATS(net, LINUX_MIB_XFRMINHDRERROR);
+		goto done;
+	}
+
+	INIT_LIST_HEAD(&sublist);
+
+	/* Handle fragment at start of payload, and/or waiting reassembly. */
+
+	blkoff = ntohs(ipth->block_offset);
+	/* check before locking i.e., maybe */
+	if (blkoff || xtfs->ra_runtlen || xtfs->ra_newskb) {
+		spin_lock(&xtfs->drop_lock);
+
+		/* check again after lock */
+		if (blkoff || xtfs->ra_runtlen || xtfs->ra_newskb) {
+			data = iptfs_reassem_cont(xtfs, seq, &skbseq, skb, data,
+						  blkoff, &sublist);
+		}
+
+		spin_unlock(&xtfs->drop_lock);
+	}
+
+	/* New packets */
+
+	tail = skb->len;
+	BUG_ON(xtfs->ra_newskb && data < tail);
+
+	while (data < tail) {
+		u32 protocol = 0;
+
+		/* Gather information on the next data block.
+		 * `data` points to the start of the data block.
+		 */
+		remaining = tail - data;
+
+		/* try and copy enough bytes to read length from ipv4/ipv6 */
+		iphlen = min_t(u32, remaining, 6);
+		if (skb_copy_bits_seq(&skbseq, data, hbytes, iphlen)) {
+			XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);
+			goto done;
+		}
+
+		iph = (struct iphdr *)hbytes;
+		if (iph->version == 0x4) {
+			/* must have at least tot_len field present */
+			if (remaining < 4) {
+				/* save the bytes we have, advance data and exit */
+				iptfs_input_save_runt(xtfs, seq, hbytes,
+						      remaining);
+				data += remaining;
+				break;
+			}
+
+			iplen = htons(iph->tot_len);
+			iphlen = iph->ihl << 2;
+			protocol = htons(ETH_P_IP);
+			XFRM_MODE_SKB_CB(skbseq.root_skb)->tos = iph->tos;
+		} else if (iph->version == 0x6) {
+			/* must have at least payload_len field present */
+			if (remaining < 6) {
+				/* save the bytes we have, advance data and exit */
+				iptfs_input_save_runt(xtfs, seq, hbytes,
+						      remaining);
+				data += remaining;
+				break;
+			}
+
+			iplen = htons(((struct ipv6hdr *)hbytes)->payload_len);
+			iplen += sizeof(struct ipv6hdr);
+			iphlen = sizeof(struct ipv6hdr);
+			protocol = htons(ETH_P_IPV6);
+			XFRM_MODE_SKB_CB(skbseq.root_skb)->tos =
+				ipv6_get_dsfield((struct ipv6hdr *)iph);
+		} else if (iph->version == 0x0) {
+			/* pad */
+			data = tail;
+			break;
+		} else {
+			XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);
+			goto done;
+		}
+
+		if (unlikely(skbseq.stepped_offset)) {
+			/* We need to reset our seq read, it can't backup at
+			 * this point.
+			 */
+			struct sk_buff *save = skbseq.root_skb;
+
+			skb_abort_seq_read(&skbseq);
+			skb_prepare_seq_read(save, data, tail, &skbseq);
+		}
+
+		if (first_skb) {
+			skb = NULL;
+		} else {
+			first_skb = skb;
+			first_iplen = iplen;
+			fragwalk = NULL;
+
+			/* We are going to skip over `data` bytes to reach the
+			 * start of the IP header of `iphlen` len for `iplen`
+			 * inner packet.
+			 */
+
+			if (skb_has_frag_list(skb)) {
+				defer = skb;
+				skb = NULL;
+			} else if (data + iphlen <= skb_headlen(skb) &&
+				   /* make sure our header is 32-bit aligned? */
+				   /* ((uintptr_t)(skb->data + data) & 0x3) == 0 && */
+				   skb_tailroom(skb) + tail - data >= iplen) {
+				/* Reuse the received skb.
+				 *
+				 * We have enough headlen to pull past any
+				 * initial fragment data, leaving at least the
+				 * IP header in the linear buffer space.
+				 *
+				 * For linear buffer space we only require that
+				 * linear buffer space is large enough to
+				 * eventually hold the entire reassembled
+				 * packet (by including tailroom in the check).
+				 *
+				 * For non-linear tailroom is 0 and so we only
+				 * re-use if the entire packet is present
+				 * already.
+				 *
+				 * NOTE: there are many more options for
+				 * sharing, KISS for now. Also, this can produce
+				 * skb's with the IP header unaligned to 32
+				 * bits. If that ends up being a problem then a
+				 * check should be added to the conditional
+				 * above that the header lies on a 32-bit
+				 * boundary as well.
+				 */
+				skb_pull(skb, data);
+
+				/* our range just changed */
+				data = 0;
+				tail = skb->len;
+				remaining = skb->len;
+
+				skb->protocol = protocol;
+				skb_mac_header_rebuild(skb);
+				if (skb->mac_len)
+					eth_hdr(skb)->h_proto = skb->protocol;
+
+				/* all pointers could be changed now reset walk */
+				skb_abort_seq_read(&skbseq);
+				skb_prepare_seq_read(skb, data, tail, &skbseq);
+			} else if (skb->head_frag &&
+				   /* We have the IP header right now */
+				   remaining >= iphlen) {
+				fragwalk = &_fragwalk;
+				skb_prepare_frag_walk(skb, data, fragwalk);
+				defer = skb;
+				skb = NULL;
+			} else {
+				/* We couldn't reuse the input skb so allocate a
+				 * new one.
+				 */
+				defer = skb;
+				skb = NULL;
+			}
+
+			/* Don't trim `first_skb` until the end as we are
+			 * walking that data now.
+			 */
+		}
+
+		capturelen = min(iplen, remaining);
+		if (!skb) {
+			if (!fragwalk ||
+			    /* Large enough to be worth sharing */
+			    iplen < IPTFS_PKT_SHARE_MIN ||
+			    /* Have IP header + some data to share. */
+			    capturelen <= iphlen ||
+			    /* Try creating skb and adding frags */
+			    !(skb = iptfs_pskb_add_frags(first_skb, fragwalk,
+							 data, capturelen,
+							 &skbseq, iphlen))) {
+				skb = iptfs_pskb_extract_seq(iplen, &skbseq,
+							     data, capturelen);
+			}
+			if (!skb) {
+				/* skip to next packet or done */
+				data += capturelen;
+				continue;
+			}
+			BUG_ON(skb->len != capturelen);
+
+			skb->protocol = protocol;
+			if (old_mac) {
+				/* rebuild the mac header */
+				skb_set_mac_header(skb, -first_skb->mac_len);
+				memcpy(skb_mac_header(skb), old_mac,
+				       first_skb->mac_len);
+				eth_hdr(skb)->h_proto = skb->protocol;
+			}
+		}
+
+		data += capturelen;
+
+		if (skb->len < iplen) {
+			BUG_ON(data != tail);
+			BUG_ON(xtfs->ra_newskb);
+
+			/* Start reassembly */
+			spin_lock(&xtfs->drop_lock);
+
+			xtfs->ra_newskb = skb;
+			xtfs->ra_wantseq = seq + 1;
+			if (!hrtimer_is_queued(&xtfs->drop_timer)) {
+				/* softirq blocked lest the timer fire and interrupt us */
+				BUG_ON(!in_interrupt());
+				hrtimer_start(&xtfs->drop_timer,
+					      xtfs->drop_time_ns,
+					      IPTFS_HRTIMER_MODE);
+			}
+
+			spin_unlock(&xtfs->drop_lock);
+
+			break;
+		}
+
+		iptfs_complete_inner_skb(x, skb);
+		list_add_tail(&skb->list, &sublist);
+	}
+
+	if (data != tail)
+		/* this should not happen from the above code */
+		XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMINIPTFSERROR);
+
+	if (first_skb && first_iplen && !defer && first_skb != xtfs->ra_newskb) {
+		/* first_skb is queued b/c !defer and not partial */
+		if (pskb_trim(first_skb, first_iplen)) {
+			/* error trimming */
+			list_del(&first_skb->list);
+			defer = first_skb;
+		}
+		first_skb->ip_summed = CHECKSUM_NONE;
+	}
+
+	/* Send the packets! */
+	list_for_each_entry_safe(skb, next, &sublist, list) {
+		BUG_ON(skb == defer);
+		skb_list_del_init(skb);
+		if (xfrm_input(skb, 0, 0, -3))
+			kfree_skb(skb);
+	}
+
+done:
+	skb = skbseq.root_skb;
+	skb_abort_seq_read(&skbseq);
+
+	if (defer) {
+		consume_skb(defer);
+	} else if (!first_skb) {
+		/* skb is the original passed in skb, but we didn't get far
+		 * enough to process it as the first_skb, if we had it would
+		 * either be save in ra_newskb, trimmed and sent on as an skb or
+		 * placed in defer to be freed.
+		 */
+		BUG_ON(!skb);
+		kfree_skb(skb);
+	}
+
+	return 0;
+}
+
+/* ------------------------------- */
+/* Input (Egress) Re-ordering Code */
+/* ------------------------------- */
+
+static void __vec_shift(struct xfrm_iptfs_data *xtfs, u32 shift)
+{
+	u32 savedlen = xtfs->w_savedlen;
+
+	if (shift > savedlen)
+		shift = savedlen;
+	if (shift != savedlen)
+		memcpy(xtfs->w_saved, xtfs->w_saved + shift,
+		       (savedlen - shift) * sizeof(*xtfs->w_saved));
+	memset(xtfs->w_saved + savedlen - shift, 0,
+	       shift * sizeof(*xtfs->w_saved));
+	xtfs->w_savedlen -= shift;
+}
+
+static int __reorder_past(struct xfrm_iptfs_data *xtfs, struct sk_buff *inskb,
+			  struct list_head *freelist, u32 *fcount)
+{
+	list_add_tail(&inskb->list, freelist);
+	(*fcount)++;
+	return 0;
+}
+
+static u32 __reorder_drop(struct xfrm_iptfs_data *xtfs, struct list_head *list)
+
+{
+	struct skb_wseq *s, *se;
+	const u32 savedlen = xtfs->w_savedlen;
+	u64 wantseq = xtfs->w_wantseq;
+	time64_t now = ktime_get_raw_fast_ns();
+	u32 count = 0;
+	u32 scount = 0;
+
+	BUG_ON(!savedlen);
+	if (xtfs->w_saved[0].drop_time > now)
+		goto set_timer;
+
+	wantseq = ++xtfs->w_wantseq;
+
+	/* Keep flushing packets until we reach a drop time greater than now. */
+	s = xtfs->w_saved;
+	se = s + savedlen;
+	do {
+		/* Walking past empty slots until we reach a packet */
+		for (; s < se && !s->skb; s++)
+			if (s->drop_time > now)
+				goto outerdone;
+		/* Sending packets until we hit another empty slot. */
+		for (; s < se && s->skb; scount++, s++)
+			list_add_tail(&s->skb->list, list);
+	} while (s < se);
+outerdone:
+
+	count = s - xtfs->w_saved;
+	if (count) {
+		xtfs->w_wantseq += count;
+
+		/* Shift handled slots plus final empty slot into slot 0. */
+		__vec_shift(xtfs, count);
+	}
+
+	if (xtfs->w_savedlen) {
+set_timer:
+		/* Drifting is OK */
+		hrtimer_start(&xtfs->drop_timer,
+			      xtfs->w_saved[0].drop_time - now,
+			      IPTFS_HRTIMER_MODE);
+	}
+	return scount;
+}
+
+static u32 __reorder_this(struct xfrm_iptfs_data *xtfs, struct sk_buff *inskb,
+			  struct list_head *list)
+
+{
+	struct skb_wseq *s, *se;
+	const u32 savedlen = xtfs->w_savedlen;
+	u64 wantseq = xtfs->w_wantseq;
+	u32 count = 0;
+
+	/* Got what we wanted. */
+	list_add_tail(&inskb->list, list);
+	wantseq = ++xtfs->w_wantseq;
+	if (!savedlen)
+		return 1;
+
+	/* Flush remaining consecutive packets. */
+
+	/* Keep sending until we hit another missed pkt. */
+	for (s = xtfs->w_saved, se = s + savedlen; s < se && s->skb; s++)
+		list_add_tail(&s->skb->list, list);
+	count = s - xtfs->w_saved;
+	if (count)
+		xtfs->w_wantseq += count;
+
+	/* Shift handled slots plus final empty slot into slot 0. */
+	__vec_shift(xtfs, count + 1);
+
+	return count + 1;
+}
+
+/* Set the slot's drop time and all the empty slots below it until reaching a
+ * filled slot which will already be set.
+ */
+static void iptfs_set_window_drop_times(struct xfrm_iptfs_data *xtfs, int index)
+{
+	const u32 savedlen = xtfs->w_savedlen;
+	struct skb_wseq *s = xtfs->w_saved;
+	time64_t drop_time;
+
+	assert_spin_locked(&xtfs->drop_lock);
+
+	if (savedlen > index + 1) {
+		/* we are below another, our drop time and the timer are already set */
+		BUG_ON(xtfs->w_saved[index + 1].drop_time !=
+		       xtfs->w_saved[index].drop_time);
+		return;
+	}
+	/* we are the most future so get a new drop time. */
+	drop_time = ktime_get_raw_fast_ns();
+	drop_time += xtfs->drop_time_ns;
+
+	/* Walk back through the array setting drop times as we go */
+	s[index].drop_time = drop_time;
+	while (index-- > 0 && !s[index].skb)
+		s[index].drop_time = drop_time;
+
+	/* If we walked all the way back, schedule the drop timer if needed */
+	if (index == -1 && !hrtimer_is_queued(&xtfs->drop_timer))
+		hrtimer_start(&xtfs->drop_timer, xtfs->drop_time_ns,
+			      IPTFS_HRTIMER_MODE);
+}
+
+static u32 __reorder_future_fits(struct xfrm_iptfs_data *xtfs,
+				 struct sk_buff *inskb,
+				 struct list_head *freelist, u32 *fcount)
+{
+	const u32 nslots = xtfs->cfg.reorder_win_size + 1;
+	const u64 inseq = __esp_seq(inskb);
+	const u64 wantseq = xtfs->w_wantseq;
+	const u64 distance = inseq - wantseq;
+	const u32 savedlen = xtfs->w_savedlen;
+	const u32 index = distance - 1;
+
+	BUG_ON(distance >= nslots);
+
+	/* Handle future sequence number received which fits in the window.
+	 *
+	 * We know we don't have the seq we want so we won't be able to flush
+	 * anything.
+	 */
+
+	/* slot count is 4, saved size is 3 savedlen is 2
+	 *
+	 * "window boundary" is based on the fixed window size
+	 * distance is also slot number
+	 * index is an array index (i.e., - 1 of slot)
+	 * : : - implicit NULL after array len
+	 *
+	 *          +--------- used length (savedlen == 2)
+	 *          |   +----- array size (nslots - 1 == 3)
+	 *          |   |   + window boundary (nslots == 4)
+	 *          V   V | V
+	 *                |
+	 *  0   1   2   3 |   slot number
+	 * ---  0   1   2 |   array index
+	 *     [-] [b] : :|   array
+	 *
+	 * "2" "3" "4" *5*|   seq numbers
+	 *
+	 * We receive seq number 5
+	 * distance == 3 [inseq(5) - w_wantseq(2)]
+	 * index == 2 [distance(6) - 1]
+	 */
+
+	if (xtfs->w_saved[index].skb) {
+		/* a dup of a future */
+		list_add_tail(&inskb->list, freelist);
+		(*fcount)++;
+		return 0;
+	}
+
+	xtfs->w_saved[index].skb = inskb;
+	xtfs->w_savedlen = max(savedlen, index + 1);
+	iptfs_set_window_drop_times(xtfs, index);
+
+	return 0;
+}
+
+static u32 __reorder_future_shifts(struct xfrm_iptfs_data *xtfs,
+				   struct sk_buff *inskb,
+				   struct list_head *list,
+				   struct list_head *freelist, u32 *fcount)
+{
+	const u32 nslots = xtfs->cfg.reorder_win_size + 1;
+	const u64 inseq = __esp_seq(inskb);
+	u32 savedlen = xtfs->w_savedlen;
+	u64 wantseq = xtfs->w_wantseq;
+	struct sk_buff *slot0 = NULL;
+	u64 last_drop_seq = xtfs->w_wantseq;
+	u64 distance, extra_drops, missed, s0seq;
+	u32 count = 0;
+	struct skb_wseq *wnext;
+	u32 beyond, shifting, slot;
+
+	BUG_ON(inseq <= wantseq);
+	distance = inseq - wantseq;
+	BUG_ON(distance <= nslots - 1);
+	beyond = distance - (nslots - 1);
+	missed = 0;
+
+	/* Handle future sequence number received.
+	 *
+	 * IMPORTANT: we are at least advancing w_wantseq (i.e., wantseq) by 1
+	 * b/c we are beyond the window boundary.
+	 *
+	 * We know we don't have the wantseq so that counts as a drop.
+	 */
+
+	/* ex: slot count is 4, array size is 3 savedlen is 2, slot 0 is the
+	 * missing sequence number.
+	 *
+	 * the final slot at savedlen (index savedlen - 1) is always occupied.
+	 *
+	 * beyond is "beyond array size" not savedlen.
+	 *
+	 *          +--------- array length (savedlen == 2)
+	 *          |   +----- array size (nslots - 1 == 3)
+	 *          |   |   +- window boundary (nslots == 4)
+	 *          V   V | V
+	 *                |
+	 *  0   1   2   3 |   slot number
+	 * ---  0   1   2 |   array index
+	 *     [b] [c] : :|   array
+	 *                |
+	 * "2" "3" "4" "5"|*6*  seq numbers
+	 *
+	 * We receive seq number 6
+	 * distance == 4 [inseq(6) - w_wantseq(2)]
+	 * newslot == distance
+	 * index == 3 [distance(4) - 1]
+	 * beyond == 1 [newslot(4) - lastslot((nslots(4) - 1))]
+	 * shifting == 1 [min(savedlen(2), beyond(1)]
+	 * slot0_skb == [b], and should match w_wantseq
+	 *
+	 *                +--- window boundary (nslots == 4)
+	 *  0   1   2   3 | 4   slot number
+	 * ---  0   1   2 | 3   array index
+	 *     [b] : : : :|     array
+	 * "2" "3" "4" "5" *6*  seq numbers
+	 *
+	 * We receive seq number 6
+	 * distance == 4 [inseq(6) - w_wantseq(2)]
+	 * newslot == distance
+	 * index == 3 [distance(4) - 1]
+	 * beyond == 1 [newslot(4) - lastslot((nslots(4) - 1))]
+	 * shifting == 1 [min(savedlen(1), beyond(1)]
+	 * slot0_skb == [b] and should match w_wantseq
+	 *
+	 *                +-- window boundary (nslots == 4)
+	 *  0   1   2   3 | 4   5   6   slot number
+	 * ---  0   1   2 | 3   4   5   array index
+	 *     [-] [c] : :|             array
+	 * "2" "3" "4" "5" "6" "7" *8*  seq numbers
+	 *
+	 * savedlen = 2, beyond = 3
+	 * iter 1: slot0 == NULL, missed++, lastdrop = 2 (2+1-1), slot0 = [-]
+	 * iter 2: slot0 == NULL, missed++, lastdrop = 3 (2+2-1), slot0 = [c]
+	 * 2 < 3, extra = 1 (3-2), missed += extra, lastdrop = 4 (2+2+1-1)
+	 *
+	 * We receive seq number 8
+	 * distance == 6 [inseq(8) - w_wantseq(2)]
+	 * newslot == distance
+	 * index == 5 [distance(6) - 1]
+	 * beyond == 3 [newslot(6) - lastslot((nslots(4) - 1))]
+	 * shifting == 2 [min(savedlen(2), beyond(3)]
+	 *
+	 * slot0_skb == NULL changed from [b] when "savedlen < beyond" is true.
+	 */
+
+	/* Now send any packets that are being shifted out of saved, and account
+	 * for missing packets that are exiting the window as we shift it.
+	 */
+
+	/* If savedlen > beyond we are shifting some, else all. */
+	shifting = min(savedlen, beyond);
+
+	/* slot0 is the buf that just shifted out and into slot0 */
+	slot0 = NULL;
+	s0seq = wantseq;
+	last_drop_seq = s0seq;
+	wnext = xtfs->w_saved;
+	for (slot = 1; slot <= shifting; slot++, wnext++) {
+		/* handle what was in slot0 before we occupy it */
+		if (!slot0) {
+			last_drop_seq = s0seq;
+			missed++;
+		} else {
+			list_add_tail(&slot0->list, list);
+			count++;
+		}
+		s0seq++;
+		slot0 = wnext->skb;
+		wnext->skb = NULL;
+	}
+
+	/* slot0 is now either NULL (in which case it's what we now are waiting
+	 * for, or a buf in which case we need to handle it like we received it;
+	 * however, we may be advancing past that buffer as well..
+	 */
+
+	/* Handle case where we need to shift more than we had saved, slot0 will
+	 * be NULL iff savedlen is 0, otherwise slot0 will always be
+	 * non-NULL b/c we shifted the final element, which is always set if
+	 * there is any saved, into slot0.
+	 */
+	if (savedlen < beyond) {
+		extra_drops = beyond - savedlen;
+		if (savedlen == 0) {
+			BUG_ON(slot0);
+			s0seq += extra_drops;
+			last_drop_seq = s0seq - 1;
+		} else {
+			extra_drops--; /* we aren't dropping what's in slot0 */
+			BUG_ON(!slot0);
+			list_add_tail(&slot0->list, list);
+			/* if extra_drops then we are going past this slot0
+			 * so we can safely advance last_drop_seq
+			 */
+			if (extra_drops)
+				last_drop_seq = s0seq + extra_drops;
+			s0seq += extra_drops + 1;
+			count++;
+		}
+		missed += extra_drops;
+		slot0 = NULL;
+		/* slot0 has had an empty slot pushed into it */
+	}
+
+	/* Remove the entries */
+	__vec_shift(xtfs, beyond);
+
+	/* Advance want seq */
+	xtfs->w_wantseq += beyond;
+
+	/* Process drops here when implementing congestion control */
+
+	/* We've shifted. plug the packet in at the end. */
+	xtfs->w_savedlen = nslots - 1;
+	xtfs->w_saved[xtfs->w_savedlen - 1].skb = inskb;
+	iptfs_set_window_drop_times(xtfs, xtfs->w_savedlen - 1);
+
+	/* if we don't have a slot0 then we must wait for it */
+	if (!slot0)
+		return count;
+
+	/* If slot0, seq must match new want seq */
+	BUG_ON(xtfs->w_wantseq != __esp_seq(slot0));
+
+	/* slot0 is valid, treat like we received expected. */
+	count += __reorder_this(xtfs, slot0, list);
+	return count;
+}
+
+/* Receive a new packet into the reorder window. Return a list of ordered
+ * packets from the window.
+ */
+static u32 iptfs_input_reorder(struct xfrm_iptfs_data *xtfs,
+			       struct sk_buff *inskb, struct list_head *list,
+			       struct list_head *freelist, u32 *fcount)
+{
+	const u32 nslots = xtfs->cfg.reorder_win_size + 1;
+	u64 inseq = __esp_seq(inskb);
+	u64 wantseq;
+
+	assert_spin_locked(&xtfs->drop_lock);
+
+	if (unlikely(!xtfs->w_seq_set)) {
+		xtfs->w_seq_set = true;
+		xtfs->w_wantseq = inseq;
+	}
+	wantseq = xtfs->w_wantseq;
+
+	if (likely(inseq == wantseq))
+		return __reorder_this(xtfs, inskb, list);
+	else if (inseq < wantseq)
+		return __reorder_past(xtfs, inskb, freelist, fcount);
+	else if ((inseq - wantseq) < nslots)
+		return __reorder_future_fits(xtfs, inskb, freelist, fcount);
+	else
+		return __reorder_future_shifts(xtfs, inskb, list, freelist,
+					       fcount);
+}
+
+/**
+ * iptfs_drop_timer() - Handle drop timer expiry.
+ *
+ * This is similar to our input function.
+ *
+ * The drop timer is set when we start an in progress reassembly, and also when
+ * we save a future packet in the window saved array.
+ *
+ * NOTE packets in the save window are always newer WRT drop times as
+ * they get further in the future. i.e. for:
+ *
+ *    if slots (S0, S1, ... Sn) and `Dn` is the drop time for slot `Sn`,
+ *    then D(n-1) <= D(n).
+ *
+ * So, regardless of why the timer is firing we can always discard any inprogress
+ * fragment; either it's the reassembly timer, or slot 0 is going to be
+ * dropped as S0 must have the most recent drop time, and slot 0 holds the
+ * continuation fragment of the in progress packet.
+ */
+static enum hrtimer_restart iptfs_drop_timer(struct hrtimer *me)
+{
+	struct sk_buff *skb, *next;
+	struct list_head freelist, list;
+	struct xfrm_iptfs_data *xtfs;
+	struct xfrm_state *x;
+	u32 count, fcount;
+
+	xtfs = container_of(me, typeof(*xtfs), drop_timer);
+	x = xtfs->x;
+
+	spin_lock(&xtfs->drop_lock);
+
+	INIT_LIST_HEAD(&list);
+	INIT_LIST_HEAD(&freelist);
+	fcount = 0;
+
+	/* Drop any in progress packet */
+
+	if (xtfs->ra_newskb) {
+		kfree_skb(xtfs->ra_newskb);
+		xtfs->ra_newskb = NULL;
+	}
+
+	/* Now drop as many packets as we should from the reordering window
+	 * saved array
+	 */
+	count = xtfs->w_savedlen ? __reorder_drop(xtfs, &list) : 0;
+
+	spin_unlock(&xtfs->drop_lock);
+
+	if (count) {
+		list_for_each_entry_safe(skb, next, &list, list) {
+			skb_list_del_init(skb);
+			(void)iptfs_input_ordered(x, skb);
+		}
+	}
+	return HRTIMER_NORESTART;
+}
+
+/**
+ * iptfs_input() - handle receipt of iptfs payload
+ * @x: xfrm state.
+ * @skb: the packet.
+ *
+ * We have an IPTFS payload order it if needed, then process newly in order
+ * packetsA.
+ */
+static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct list_head freelist, list;
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+	struct sk_buff *next;
+	u32 count, fcount;
+
+	/* Fast path for no reorder window. */
+	if (xtfs->cfg.reorder_win_size == 0) {
+		iptfs_input_ordered(x, skb);
+		goto done;
+	}
+
+	/* Fetch list of in-order packets from the reordering window as well as
+	 * a list of buffers we need to now free.
+	 */
+	INIT_LIST_HEAD(&list);
+	INIT_LIST_HEAD(&freelist);
+	fcount = 0;
+
+	spin_lock(&xtfs->drop_lock);
+	count = iptfs_input_reorder(xtfs, skb, &list, &freelist, &fcount);
+	spin_unlock(&xtfs->drop_lock);
+
+	if (count) {
+		list_for_each_entry_safe(skb, next, &list, list) {
+			skb_list_del_init(skb);
+			(void)iptfs_input_ordered(x, skb);
+		}
+	}
+
+	if (fcount) {
+		list_for_each_entry_safe(skb, next, &freelist, list) {
+			skb_list_del_init(skb);
+			kfree_skb(skb);
+		}
+	}
+done:
+	/* We always have dealt with the input SKB, either we are re-using it,
+	 * or we have freed it. Return EINPROGRESS so that xfrm_input stops
+	 * processing it.
+	 */
+	return -EINPROGRESS;
+}
+
+/* ================================= */
+/* IPTFS Sending (ingress) Functions */
+/* ================================= */
+
+/* ------------------------- */
+/* Enqueue to send functions */
+/* ------------------------- */
+
+/**
+ * iptfs_enqueue() - enqueue packet if ok to send.
+ * @xtfs: xtfs state
+ * @skb: the packet
+ *
+ * Return: true if packet enqueued.
+ */
+static bool iptfs_enqueue(struct xfrm_iptfs_data *xtfs, struct sk_buff *skb)
+{
+	u64 newsz = xtfs->queue_size + skb->len;
+	struct iphdr *iph;
+
+	assert_spin_locked(&xtfs->x->lock);
+
+	if (newsz > xtfs->cfg.max_queue_size)
+		return false;
+
+	/* Set ECN CE if we are above our ECN queue threshold */
+	if (newsz > xtfs->ecn_queue_size) {
+		iph = ip_hdr(skb);
+		if (iph->version == 4)
+			IP_ECN_set_ce(iph);
+		else if (iph->version == 6)
+			IP6_ECN_set_ce(skb, ipv6_hdr(skb));
+	}
+
+	__skb_queue_tail(&xtfs->queue, skb);
+	xtfs->queue_size += skb->len;
+	return true;
+}
+
+static int iptfs_get_cur_pmtu(struct xfrm_state *x, struct xfrm_iptfs_data *xtfs,
+			      struct sk_buff *skb)
+{
+	struct xfrm_dst *xdst = (struct xfrm_dst *)skb_dst(skb);
+	u32 payload_mtu = xtfs->payload_mtu;
+	u32 pmtu = __iptfs_get_inner_mtu(x, xdst->child_mtu_cached);
+
+	if (payload_mtu && payload_mtu < pmtu)
+		pmtu = payload_mtu;
+
+	return pmtu;
+}
+
+static int iptfs_is_too_big(struct sock *sk, struct sk_buff *skb, u32 pmtu)
+{
+	if (skb->len <= pmtu)
+		return 0;
+
+	/* We only send ICMP too big if the user has configured us as
+	 * dont-fragment.
+	 */
+	XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMOUTERROR);
+
+	if (sk) {
+		xfrm_local_error(skb, pmtu);
+	} else if (ip_hdr(skb)->version == 4) {
+		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+			  htonl(pmtu));
+	} else {
+		WARN_ON_ONCE(ip_hdr(skb)->version != 6);
+		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, pmtu);
+	}
+	return 1;
+}
+
+/* IPv4/IPv6 packet ingress to IPTFS tunnel, arrange to send in IPTFS payload
+ * (i.e., aggregating or fragmenting as appropriate).
+ * This is set in dst->output for an SA.
+ */
+static int iptfs_output_collect(struct net *net, struct sock *sk,
+				struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct xfrm_state *x = dst->xfrm;
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+	struct sk_buff *segs, *nskb;
+	u32 count, qcount;
+	u32 pmtu = 0;
+	bool ok = true;
+	bool was_gso;
+
+	/* We have hooked into dst_entry->output which means we have skipped the
+	 * protocol specific netfilter (see xfrm4_output, xfrm6_output).
+	 * when our timer runs we will end up calling xfrm_output directly on
+	 * the encapsulated traffic.
+	 *
+	 * For both cases this is the NF_INET_POST_ROUTING hook which allows
+	 * changing the skb->dst entry which then may not be xfrm based anymore
+	 * in which case a REROUTED flag is set. and dst_output is called.
+	 *
+	 * For IPv6 we are also skipping fragmentation handling for local
+	 * sockets, which may or may not be good depending on our tunnel DF
+	 * setting. Normally with fragmentation supported we want to skip this
+	 * fragmentation.
+	 */
+
+	BUG_ON(!xtfs);
+
+	if (xtfs->cfg.dont_frag)
+		pmtu = iptfs_get_cur_pmtu(x, xtfs, skb);
+
+	/* Break apart GSO skbs. If the queue is nearing full then we want the
+	 * accounting and queuing to be based on the individual packets not on the
+	 * aggregate GSO buffer.
+	 */
+	was_gso = skb_is_gso(skb);
+	if (!was_gso) {
+		segs = skb;
+	} else {
+		segs = skb_gso_segment(skb, 0);
+		if (IS_ERR_OR_NULL(segs)) {
+			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
+			kfree_skb(skb);
+			return PTR_ERR(segs);
+		}
+		consume_skb(skb);
+		skb = NULL;
+	}
+
+	count = 0;
+	qcount = 0;
+
+	/* We can be running on multiple cores and from the network softirq or
+	 * from user context depending on where the packet is coming from.
+	 */
+	spin_lock_bh(&x->lock);
+
+	skb_list_walk_safe(segs, skb, nskb) {
+		skb_mark_not_on_list(skb);
+		count++;
+
+		/* Once we drop due to no queue space we continue to drop the
+		 * rest of the packets from that GRO.
+		 */
+		if (!ok) {
+nospace:
+			trace_iptfs_no_queue_space(skb, xtfs, pmtu, was_gso);
+			XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMOUTNOQSPACE);
+			kfree_skb_reason(skb, SKB_DROP_REASON_FULL_RING);
+			continue;
+		}
+
+		/* If the user indicated no iptfs fragmenting check before
+		 * enqueue.
+		 */
+		if (xtfs->cfg.dont_frag && iptfs_is_too_big(sk, skb, pmtu)) {
+			trace_iptfs_too_big(skb, xtfs, pmtu, was_gso);
+			kfree_skb_reason(skb, SKB_DROP_REASON_PKT_TOO_BIG);
+			continue;
+		}
+
+		/* Enqueue to send in tunnel */
+
+		ok = iptfs_enqueue(xtfs, skb);
+		if (!ok)
+			goto nospace;
+
+		trace_iptfs_enqueue(skb, xtfs, pmtu, was_gso);
+		qcount++;
+	}
+
+	/* Start a delay timer if we don't have one yet */
+	if (!hrtimer_is_queued(&xtfs->iptfs_timer)) {
+		/* softirq blocked lest the timer fire and interrupt us */
+		BUG_ON(!in_interrupt());
+		hrtimer_start(&xtfs->iptfs_timer, xtfs->init_delay_ns,
+			      IPTFS_HRTIMER_MODE);
+
+		xtfs->iptfs_settime = ktime_get_raw_fast_ns();
+		trace_iptfs_timer_start(xtfs, xtfs->init_delay_ns);
+	}
+
+	spin_unlock_bh(&x->lock);
+	return 0;
+}
+
+/* -------------------------- */
+/* Dequeue and send functions */
+/* -------------------------- */
+
+static void iptfs_output_prepare_skb(struct sk_buff *skb, u32 blkoff)
+{
+	struct ip_iptfs_hdr *h;
+	size_t hsz = sizeof(*h);
+
+	/* now reset values to be pointing at the rest of the packets */
+	h = skb_push(skb, hsz);
+	memset(h, 0, hsz);
+	if (blkoff)
+		h->block_offset = htons(blkoff);
+
+	/* network_header current points at the inner IP packet
+	 * move it to the iptfs header
+	 */
+	skb->transport_header = skb->network_header;
+	skb->network_header -= hsz;
+
+	IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
+
+	/* xfrm[46]_prepare_output sets skb->protocol here, but the resulting
+	 * called ip[6]_output functions also set this value as appropriate so
+	 * seems unnecessary
+	 *
+	 * skb->protocol = htons(ETH_P_IP) or htons(ETH_P_IPV6);
+	 */
+}
+
+/**
+ * iptfs_copy_create_frag() - create an inner fragment skb.
+ * @st: The source packet data.
+ * @offset: offset in @st of the new fragment data.
+ * @copy_len: the amount of data to copy from @st.
+ *
+ * Create a new skb holding a single IPTFS inner packet fragment. @copy_len must
+ * not be greater than the max fragment size.
+ *
+ * Return: the new fragment skb or an ERR_PTR().
+ */
+static struct sk_buff *iptfs_copy_create_frag(struct skb_seq_state *st,
+					      u32 offset, u32 copy_len)
+{
+	struct sk_buff *src = st->root_skb;
+	struct sk_buff *skb;
+	int err;
+
+	skb = iptfs_alloc_skb(src, copy_len, true);
+	if (!skb)
+		return ERR_PTR(-ENOMEM);
+
+	/* Now copy `copy_len` data from src */
+	err = skb_copy_bits_seq(st, offset, skb_put(skb, copy_len), copy_len);
+	if (err) {
+		XFRM_INC_STATS(dev_net(src->dev), LINUX_MIB_XFRMOUTERROR);
+		kfree_skb(skb);
+		return ERR_PTR(err);
+	}
+
+	return skb;
+}
+
+/**
+ * iptfs_copy_create_frags() - create and send N-1 fragments of a larger skb.
+ * @skbp: the source packet skb (IN), skb holding the last fragment in
+ *        the fragment stream (OUT).
+ * @xtfs: IPTFS SA state.
+ * @mtu: the max IPTFS fragment size.
+ *
+ * This function is responsible for fragmenting a larger inner packet into a
+ * sequence of IPTFS payload packets. The last fragment is returned rather than
+ * being sent so that the caller can append more inner packets (aggregation) if
+ * there is room.
+ */
+static int iptfs_copy_create_frags(struct sk_buff **skbp,
+				   struct xfrm_iptfs_data *xtfs, u32 mtu)
+{
+	struct skb_seq_state skbseq;
+	struct list_head sublist;
+	struct sk_buff *skb = *skbp;
+	struct sk_buff *nskb = *skbp;
+	u32 copy_len, offset;
+	u32 to_copy = skb->len - mtu;
+	u32 blkoff = 0;
+	int err = 0;
+
+	INIT_LIST_HEAD(&sublist);
+
+	BUG_ON(skb->len <= mtu);
+	skb_prepare_seq_read(skb, 0, skb->len, &skbseq);
+
+	/* A trimmed `skb` will be sent as the first fragment, later. */
+	offset = mtu;
+	to_copy = skb->len - offset;
+	while (to_copy) {
+		/* Send all but last fragment to allow agg. append */
+		trace_iptfs_first_fragmenting(nskb, mtu, to_copy, NULL);
+		list_add_tail(&nskb->list, &sublist);
+
+		/* FUTURE: if the packet has an odd/non-aligning length we could
+		 * send less data in the penultimate fragment so that the last
+		 * fragment then ends on an aligned boundary.
+		 */
+		copy_len = to_copy <= mtu ? to_copy : mtu;
+		nskb = iptfs_copy_create_frag(&skbseq, offset, copy_len);
+		if (IS_ERR(nskb)) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMOUTERROR);
+			skb_abort_seq_read(&skbseq);
+			err = PTR_ERR(nskb);
+			nskb = NULL;
+			break;
+		}
+		iptfs_output_prepare_skb(nskb, to_copy);
+		offset += copy_len;
+		to_copy -= copy_len;
+		blkoff = to_copy;
+	}
+	skb_abort_seq_read(&skbseq);
+
+	/* return last fragment that will be unsent (or NULL) */
+	*skbp = nskb;
+	if (nskb)
+		trace_iptfs_first_final_fragment(nskb, mtu, blkoff, NULL);
+
+	/* trim the original skb to MTU */
+	if (!err)
+		err = pskb_trim(skb, mtu);
+
+	if (err) {
+		/* Free all frags. Don't bother sending a partial packet we will
+		 * never complete.
+		 */
+		kfree_skb(nskb);
+		list_for_each_entry_safe(skb, nskb, &sublist, list) {
+			skb_list_del_init(skb);
+			kfree_skb(skb);
+		}
+		return err;
+	}
+
+	/* prepare the initial fragment with an iptfs header */
+	iptfs_output_prepare_skb(skb, 0);
+
+	/* Send all but last fragment. */
+	list_for_each_entry_safe(skb, nskb, &sublist, list) {
+		skb_list_del_init(skb);
+		xfrm_output(NULL, skb);
+	}
+
+	return 0;
+}
+
+/**
+ * iptfs_first_should_copy() - determine if we should copy packet data.
+ * @first_skb: the first skb in the packet
+ * @mtu: the MTU.
+ *
+ * Determine if we should create subsequent skbs to hold the remaining data from
+ * a large inner packet by copying the packet data, or cloning the original skb
+ * and adjusting the offsets.
+ */
+static bool iptfs_first_should_copy(struct sk_buff *first_skb, u32 mtu)
+{
+	u32 frag_copy_max;
+
+	/* If we have less than frag_copy_max for remaining packet we copy
+	 * those tail bytes as it is more efficient.
+	 */
+	frag_copy_max = mtu <= IPTFS_FRAG_COPY_MAX ? mtu : IPTFS_FRAG_COPY_MAX;
+	if ((int)first_skb->len - (int)mtu < (int)frag_copy_max)
+		return true;
+
+	/* If we have non-linear skb just use copy */
+	if (skb_is_nonlinear(first_skb))
+		return true;
+
+	/* So we have a simple linear skb, easy to clone and share */
+	return false;
+}
+
+/**
+ * iptfs_first_skb() - handle the first dequeued inner packet for output
+ * @skbp: the source packet skb (IN), skb holding the last fragment in
+ *        the fragment stream (OUT).
+ * @xtfs: IPTFS SA state.
+ * @mtu: the max IPTFS fragment size.
+ *
+ * This function is responsible for fragmenting a larger inner packet into a
+ * sequence of IPTFS payload packets. If it needs to fragment into subsequent
+ * skb's, it will either do so by copying or cloning.
+ *
+ * The last fragment is returned rather than being sent so that the caller can
+ * append more inner packets (aggregation) if there is room.
+ *
+ */
+static int iptfs_first_skb(struct sk_buff **skbp, struct xfrm_iptfs_data *xtfs,
+			   u32 mtu)
+{
+	struct sk_buff *skb = *skbp;
+	int err;
+
+	/* Classic ESP skips the don't fragment ICMP error if DF is clear on
+	 * the inner packet or ignore_df is set. Otherwise it will send an ICMP
+	 * or local error if the inner packet won't fit it's MTU.
+	 *
+	 * With IPTFS we do not care about the inner packet DF bit. If the
+	 * tunnel is configured to "don't fragment" we error back if things
+	 * don't fit in our max packet size. Otherwise we iptfs-fragment as
+	 * normal.
+	 */
+
+	/* The opportunity for HW offload has ended */
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		err = skb_checksum_help(skb);
+		if (err)
+			return err;
+	}
+
+	/* We've split these up before queuing */
+	BUG_ON(skb_is_gso(skb));
+
+	trace_iptfs_first_dequeue(skb, mtu, 0, ip_hdr(skb));
+
+	/* Simple case -- it fits. `mtu` accounted for all the overhead
+	 * including the basic IPTFS header.
+	 */
+	if (skb->len <= mtu) {
+		iptfs_output_prepare_skb(skb, 0);
+		return 0;
+	}
+
+	BUG_ON(xtfs->cfg.dont_frag);
+
+	if (iptfs_first_should_copy(skb, mtu))
+		return iptfs_copy_create_frags(skbp, xtfs, mtu);
+
+	/* For now we always copy */
+	return iptfs_copy_create_frags(skbp, xtfs, mtu);
+}
+
+static struct sk_buff **iptfs_rehome_fraglist(struct sk_buff **nextp,
+					      struct sk_buff *child)
+{
+	u32 fllen = 0;
+
+	BUG_ON(!skb_has_frag_list(child));
+
+	/* It might be possible to account for a frag list in addition to page
+	 * fragment if it's a valid state to be in. The page fragments size
+	 * should be kept as data_len so only the frag_list size is removed,
+	 * this must be done above as well took
+	 */
+	BUG_ON(skb_shinfo(child)->nr_frags);
+	*nextp = skb_shinfo(child)->frag_list;
+	while (*nextp) {
+		fllen += (*nextp)->len;
+		nextp = &(*nextp)->next;
+	}
+	skb_frag_list_init(child);
+	BUG_ON(fllen > child->data_len);
+	child->len -= fllen;
+	child->data_len -= fllen;
+
+	return nextp;
+}
+
+static void iptfs_consume_frags(struct sk_buff *to, struct sk_buff *from)
+{
+	struct skb_shared_info *fromi = skb_shinfo(from);
+	struct skb_shared_info *toi = skb_shinfo(to);
+	unsigned int new_truesize;
+
+	/* If we have data in a head page, grab it */
+	if (!skb_headlen(from)) {
+		new_truesize = SKB_TRUESIZE(skb_end_offset(from));
+	} else {
+		skb_head_to_frag(from, &toi->frags[toi->nr_frags]);
+		skb_frag_ref(to, toi->nr_frags++);
+		new_truesize = SKB_DATA_ALIGN(sizeof(struct sk_buff));
+	}
+
+	/* Move any other page fragments rather than copy */
+	memcpy(&toi->frags[toi->nr_frags], fromi->frags,
+	       sizeof(fromi->frags[0]) * fromi->nr_frags);
+	toi->nr_frags += fromi->nr_frags;
+	fromi->nr_frags = 0;
+	from->data_len = 0;
+	from->len = 0;
+	to->truesize += from->truesize - new_truesize;
+	from->truesize = new_truesize;
+
+	/* We are done with this SKB */
+	consume_skb(from);
+}
+
+static void iptfs_output_queued(struct xfrm_state *x, struct sk_buff_head *list)
+{
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+	u32 payload_mtu = xtfs->payload_mtu;
+	struct sk_buff *skb, *skb2, **nextp;
+	struct skb_shared_info *shi, *shi2;
+
+	/* For now we are just outputting packets as fast as we can, so if we
+	 * are fragmenting we will do so until the last inner packet has been
+	 * consumed.
+	 *
+	 * When we are fragmenting we need to output all outer packets that
+	 * contain the fragments of a single inner packet, consecutively (ESP
+	 * seq-wise). So we need a lock to keep another CPU from sending the
+	 * next batch of packets (it's `list`) and trying to output those, while
+	 * we output our `list` resuling with interleaved non-spec-client inner
+	 * packet streams. Thus we need to lock the IPTFS output on a per SA
+	 * basis while we process this list.
+	 */
+
+	/* NOTE: for the future, for timed packet sends, if our queue is not
+	 * growing longer (i.e., we are keeping up) and a packet we are about to
+	 * fragment will not fragment in then next outer packet, we might consider
+	 * holding on to it to send whole in the next slot. The question then is
+	 * does this introduce a continuous delay in the inner packet stream
+	 * with certain packet rates and sizes?
+	 */
+
+	/* and send them on their way */
+
+	while ((skb = __skb_dequeue(list))) {
+		struct xfrm_dst *xdst = (struct xfrm_dst *)skb_dst(skb);
+		u32 mtu = __iptfs_get_inner_mtu(x, xdst->child_mtu_cached);
+		bool share_ok = true;
+		int remaining;
+
+		/* protocol comes to us cleared sometimes */
+		skb->protocol = x->outer_mode.family == AF_INET ?
+					htons(ETH_P_IP) :
+					htons(ETH_P_IPV6);
+
+		if (payload_mtu && payload_mtu < mtu)
+			mtu = payload_mtu;
+
+		if (skb->len > mtu && xtfs->cfg.dont_frag) {
+			/* We handle this case before enqueueing so we are only
+			 * here b/c MTU changed after we enqueued before we
+			 * dequeued, just drop these.
+			 */
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMOUTERROR);
+
+			trace_iptfs_first_toobig(skb, mtu, 0, ip_hdr(skb));
+			kfree_skb_reason(skb, SKB_DROP_REASON_PKT_TOO_BIG);
+			continue;
+		}
+
+		/* iptfs_first_skb will free skb on error as well */
+		if (iptfs_first_skb(&skb, xtfs, mtu))
+			continue;
+
+		/* The returned skb is the last IPTFS fragment, it has it's
+		 * IPTFS header included and it's blkoff set just past the end
+		 * fragment data if needed. The space remaining to send more
+		 * inner packet data is `mtu` - (skb->len - sizeof iptfs
+		 * header). This is b/c the `mtu` value has the basic IPTFS
+		 * header len accounted for, and we added that header to the skb
+		 * so it is a part of skb->len, thus we subtract it from the skb
+		 * length.
+		 */
+		remaining = mtu - (skb->len - sizeof(struct ip_iptfs_hdr));
+
+		/* Re-home nested fragment lists. */
+		shi = skb_shinfo(skb);
+		nextp = &shi->frag_list;
+		while (*nextp) {
+			if (skb_has_frag_list(*nextp))
+				nextp = iptfs_rehome_fraglist(&(*nextp)->next,
+							      *nextp);
+			else
+				nextp = &(*nextp)->next;
+		}
+
+		if (shi->frag_list || skb_cloned(skb) || skb_shared(skb))
+			share_ok = false;
+
+		/* See if we have enough space to simply append.
+		 *
+		 * NOTE: Maybe do not append if we will be mis-aligned,
+		 * SW-based endpoints will probably have to copy in this
+		 * case.
+		 */
+		while ((skb2 = skb_peek(list))) {
+			trace_iptfs_ingress_nth_peek(skb2, remaining);
+			if (skb2->len > remaining)
+				break;
+
+			__skb_unlink(skb2, list);
+
+			/* The opportunity for HW offload has ended, if we
+			 * don't have a cksum in the packet we need to add one
+			 * before encap and transmit.
+			 */
+			if (skb2->ip_summed == CHECKSUM_PARTIAL) {
+				if (skb_checksum_help(skb2)) {
+					XFRM_INC_STATS(dev_net(skb_dst(skb2)->dev),
+						       LINUX_MIB_XFRMOUTERROR);
+					kfree_skb(skb2);
+					continue;
+				}
+			}
+
+			/* skb->pp_recycle is passed to __skb_flag_unref for all
+			 * frag pages so we can only share pages with skb's who
+			 * match ourselves.
+			 */
+			shi2 = skb_shinfo(skb2);
+			if (share_ok &&
+			    (shi2->frag_list ||
+			     (!skb2->head_frag && skb_headlen(skb)) ||
+			     skb->pp_recycle != skb2->pp_recycle ||
+			     skb_zcopy(skb2) ||
+			     (shi->nr_frags + shi2->nr_frags + 1 > MAX_SKB_FRAGS)))
+				share_ok = false;
+
+			/* do acct so we can free skb2 in share case */
+			skb->data_len += skb2->len;
+			skb->len += skb2->len;
+			remaining -= skb2->len;
+
+			trace_iptfs_ingress_nth_add(skb2, share_ok);
+
+			if (share_ok) {
+				iptfs_consume_frags(skb, skb2);
+			} else {
+				/* link on the frag_list */
+				*nextp = skb2;
+				nextp = &skb2->next;
+				BUG_ON(*nextp);
+				if (skb_has_frag_list(skb2))
+					nextp = iptfs_rehome_fraglist(nextp,
+								      skb2);
+				skb->truesize += skb2->truesize;
+			}
+		}
+
+		/* Consider fragmenting this skb2 that didn't fit. For demand
+		 * driven variable sized IPTFS pkts, though this isn't buying
+		 * a whole lot, especially if we are doing a copy which waiting
+		 * to send in a new pkt would not.
+		 */
+
+		xfrm_output(NULL, skb);
+	}
+}
+
+static enum hrtimer_restart iptfs_delay_timer(struct hrtimer *me)
+{
+	struct sk_buff_head list;
+	struct xfrm_iptfs_data *xtfs;
+	struct xfrm_state *x;
+	time64_t settime;
+	size_t osize;
+
+	xtfs = container_of(me, typeof(*xtfs), iptfs_timer);
+	x = xtfs->x;
+
+	/* Process all the queued packets
+	 *
+	 * softirq execution order: timer > tasklet > hrtimer
+	 *
+	 * Network rx will have run before us giving one last chance to queue
+	 * ingress packets for us to process and transmit.
+	 */
+
+	spin_lock(&x->lock);
+	__skb_queue_head_init(&list);
+	skb_queue_splice_init(&xtfs->queue, &list);
+	osize = xtfs->queue_size;
+	xtfs->queue_size = 0;
+	settime = xtfs->iptfs_settime;
+	spin_unlock(&x->lock);
+
+	/* After the above unlock, packets can begin queuing again, and the
+	 * timer can be set again, from another CPU either in softirq or user
+	 * context (not from this one since we are running at softirq level
+	 * already).
+	 */
+
+	trace_iptfs_timer_expire(xtfs,
+				 (unsigned long long)(ktime_get_raw_fast_ns() - settime));
+
+	iptfs_output_queued(x, &list);
+
+	return HRTIMER_NORESTART;
+}
+
+/**
+ * iptfs_encap_add_ipv4() - add outer encaps
+ *
+ * This was originally taken from xfrm4_tunnel_encap_add. The reason for the
+ * copy is that IP-TFS/AGGFRAG can have different functionality for how to set
+ * the TOS/DSCP bits. Sets the protocol to a different value and doesn't do
+ * anything with inner headers as they aren't pointing into a normal IP
+ * singleton inner packet.
+ */
+static int iptfs_encap_add_ipv4(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct iphdr *top_iph;
+	int flags;
+
+	skb_reset_inner_network_header(skb);
+	skb_reset_inner_transport_header(skb);
+
+	skb_set_network_header(skb, -(x->props.header_len - x->props.enc_hdr_len));
+	skb->mac_header = skb->network_header + offsetof(struct iphdr, protocol);
+	skb->transport_header = skb->network_header + sizeof(*top_iph);
+
+	top_iph = ip_hdr(skb);
+	top_iph->ihl = 5;
+	top_iph->version = 4;
+	top_iph->protocol = IPPROTO_AGGFRAG;
+
+	/* As we have 0, fractional, 1 or N inner packets there's no obviously
+	 * correct DSCP mapping to inherit. ECN should be cleared per RFC9347
+	 * 3.1.
+	 */
+	top_iph->tos = 0;
+
+	flags = x->props.flags;
+	top_iph->frag_off = htons(IP_DF);
+	top_iph->ttl = ip4_dst_hoplimit(xfrm_dst_child(dst));
+	top_iph->saddr = x->props.saddr.a4;
+	top_iph->daddr = x->id.daddr.a4;
+	ip_select_ident(dev_net(dst->dev), skb, NULL);
+
+	return 0;
+}
+
+/**
+ * iptfs_encap_add_ipv6() - add outer encaps
+ *
+ * This was originally taken from xfrm6_tunnel_encap_add. The reason for the
+ * copy is that IP-TFS/AGGFRAG can have different functionality for how to set
+ * the flow label and TOS/DSCP bits. It also sets the protocol to a different
+ * value and doesn't do anything with inner headers as they aren't pointing into
+ * a normal IP singleton inner packet.
+ */
+static int iptfs_encap_add_ipv6(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct ipv6hdr *top_iph;
+	int dsfield;
+
+	skb_reset_inner_network_header(skb);
+	skb_reset_inner_transport_header(skb);
+
+	skb_set_network_header(skb,
+			       -x->props.header_len + x->props.enc_hdr_len);
+	skb->mac_header = skb->network_header +
+		offsetof(struct ipv6hdr, nexthdr);
+	skb->transport_header = skb->network_header + sizeof(*top_iph);
+
+	top_iph = ipv6_hdr(skb);
+	top_iph->version = 6;
+	top_iph->priority = 0;
+	memset(top_iph->flow_lbl, 0, sizeof(top_iph->flow_lbl));
+	top_iph->nexthdr = IPPROTO_AGGFRAG;
+
+	/* As we have 0, fractional, 1 or N inner packets there's no obviously
+	 * correct DSCP mapping to inherit. ECN should be cleared per RFC9347
+	 * 3.1.
+	 */
+	dsfield = 0;
+	ipv6_change_dsfield(top_iph, 0, dsfield);
+
+	top_iph->hop_limit = ip6_dst_hoplimit(xfrm_dst_child(dst));
+	top_iph->saddr = *(struct in6_addr *)&x->props.saddr;
+	top_iph->daddr = *(struct in6_addr *)&x->id.daddr;
+
+	return 0;
+}
+
+/**
+ * iptfs_prepare_output() -  prepare the skb for output
+ *
+ * Return: Error value, if 0 then skb values should be as follows:
+ *    - transport_header should point at ESP header
+ *    - network_header should point at Outer IP header
+ *    - mac_header should point at protocol/nexthdr of the outer IP
+ */
+static int iptfs_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
+{
+	if (x->outer_mode.family == AF_INET)
+		return iptfs_encap_add_ipv4(x, skb);
+	if (x->outer_mode.family == AF_INET6) {
+#if IS_ENABLED(CONFIG_IPV6)
+		return iptfs_encap_add_ipv6(x, skb);
+#else
+		WARN_ON_ONCE(1);
+		return -EAFNOSUPPORT;
+#endif
+	}
+	WARN_ON_ONCE(1);
+	return -EOPNOTSUPP;
+}
+
+/* ========================== */
+/* State Management Functions */
+/* ========================== */
+
+/**
+ * __iptfs_get_inner_mtu() - return inner MTU with no fragmentation.
+ */
+static u32 __iptfs_get_inner_mtu(struct xfrm_state *x, int outer_mtu)
+{
+	struct crypto_aead *aead;
+	u32 blksize;
+
+	aead = x->data;
+	blksize = ALIGN(crypto_aead_blocksize(aead), 4);
+	return ((outer_mtu - x->props.header_len - crypto_aead_authsize(aead)) &
+		~(blksize - 1)) - 2;
+}
+
+/**
+ * iptfs_get_mtu() - return the inner MTU for an IPTFS xfrm.
+ * @x:   XFRM state.
+ * @outer_mtu: Outer MTU for the encapsulated packet.
+ *
+ * Return: Correct MTU taking in to account the encap overhead.
+ */
+static u32 iptfs_get_inner_mtu(struct xfrm_state *x, int outer_mtu)
+{
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+
+	/* If not dont-frag we have no MTU */
+	if (!xtfs->cfg.dont_frag)
+		return x->outer_mode.family == AF_INET ? IP_MAX_MTU :
+							 IP6_MAX_MTU;
+	return __iptfs_get_inner_mtu(x, outer_mtu);
+}
+
+/**
+ * iptfs_user_init() - initialize the SA with IPTFS options from netlink.
+ */
+static int iptfs_user_init(struct net *net, struct xfrm_state *x,
+			   struct nlattr **attrs)
+{
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+	struct xfrm_iptfs_config *xc;
+
+	if (x->props.mode != XFRM_MODE_IPTFS)
+		return -EINVAL;
+
+	xc = &xtfs->cfg;
+	xc->reorder_win_size = net->xfrm.sysctl_iptfs_rewin;
+	xc->max_queue_size = net->xfrm.sysctl_iptfs_maxqsize;
+	xc->init_delay_us = net->xfrm.sysctl_iptfs_idelay;
+	xc->drop_time_us = net->xfrm.sysctl_iptfs_drptime;
+
+	if (attrs[XFRMA_IPTFS_DONT_FRAG])
+		xc->dont_frag = true;
+	if (attrs[XFRMA_IPTFS_REORD_WIN])
+		xc->reorder_win_size =
+			nla_get_u16(attrs[XFRMA_IPTFS_REORD_WIN]);
+	/* saved array is for saving 1..N seq nums from wantseq */
+	if (xc->reorder_win_size)
+		xtfs->w_saved = kcalloc(xc->reorder_win_size,
+					sizeof(*xtfs->w_saved), GFP_KERNEL);
+	if (attrs[XFRMA_IPTFS_PKT_SIZE]) {
+		xc->pkt_size = nla_get_u32(attrs[XFRMA_IPTFS_PKT_SIZE]);
+		if (!xc->pkt_size)
+			xtfs->payload_mtu = 0;
+		else if (xc->pkt_size > x->props.header_len)
+			xtfs->payload_mtu = xc->pkt_size - x->props.header_len;
+		else
+			return -EINVAL;
+	}
+	if (attrs[XFRMA_IPTFS_MAX_QSIZE])
+		xc->max_queue_size = nla_get_u32(attrs[XFRMA_IPTFS_MAX_QSIZE]);
+	if (attrs[XFRMA_IPTFS_DROP_TIME])
+		xc->drop_time_us = nla_get_u32(attrs[XFRMA_IPTFS_DROP_TIME]);
+	if (attrs[XFRMA_IPTFS_INIT_DELAY])
+		xc->init_delay_us = nla_get_u32(attrs[XFRMA_IPTFS_INIT_DELAY]);
+
+	xtfs->ecn_queue_size = (u64)xc->max_queue_size * 95 / 100;
+	xtfs->drop_time_ns = xc->drop_time_us * NSECS_IN_USEC;
+	xtfs->init_delay_ns = xc->init_delay_us * NSECS_IN_USEC;
+
+	return 0;
+}
+
+static int iptfs_copy_to_user(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+	struct xfrm_iptfs_config *xc = &xtfs->cfg;
+	int ret;
+
+	if (xc->dont_frag) {
+		ret = nla_put_flag(skb, XFRMA_IPTFS_DONT_FRAG);
+		if (ret)
+			return ret;
+	}
+	ret = nla_put_u16(skb, XFRMA_IPTFS_REORD_WIN, xc->reorder_win_size);
+	if (ret)
+		return ret;
+	ret = nla_put_u32(skb, XFRMA_IPTFS_PKT_SIZE, xc->pkt_size);
+	if (ret)
+		return ret;
+	ret = nla_put_u32(skb, XFRMA_IPTFS_MAX_QSIZE, xc->max_queue_size);
+	if (ret)
+		return ret;
+	ret = nla_put_u32(skb, XFRMA_IPTFS_DROP_TIME, xc->drop_time_us);
+	if (ret)
+		return ret;
+	ret = nla_put_u32(skb, XFRMA_IPTFS_INIT_DELAY, xc->init_delay_us);
+	return ret;
+}
+
+static int iptfs_create_state(struct xfrm_state *x)
+{
+	struct xfrm_iptfs_data *xtfs;
+
+	xtfs = kzalloc(sizeof(*xtfs), GFP_KERNEL);
+	if (!xtfs)
+		return -ENOMEM;
+	x->mode_data = xtfs;
+
+	xtfs->x = x;
+
+	__skb_queue_head_init(&xtfs->queue);
+	xtfs->init_delay_ns = xtfs->cfg.init_delay_us * NSECS_IN_USEC;
+	hrtimer_init(&xtfs->iptfs_timer, CLOCK_MONOTONIC, IPTFS_HRTIMER_MODE);
+	xtfs->iptfs_timer.function = iptfs_delay_timer;
+
+	xtfs->drop_time_ns = xtfs->cfg.drop_time_us * NSECS_IN_USEC;
+	spin_lock_init(&xtfs->drop_lock);
+	hrtimer_init(&xtfs->drop_timer, CLOCK_MONOTONIC, IPTFS_HRTIMER_MODE);
+	xtfs->drop_timer.function = iptfs_drop_timer;
+
+	/* Modify type (esp) adjustment values */
+
+	if (x->props.family == AF_INET)
+		x->props.header_len += sizeof(struct iphdr) + sizeof(struct ip_iptfs_hdr);
+	else if (x->props.family == AF_INET6)
+		x->props.header_len += sizeof(struct ipv6hdr) + sizeof(struct ip_iptfs_hdr);
+	x->props.enc_hdr_len = sizeof(struct ip_iptfs_hdr);
+
+	return 0;
+}
+
+static void iptfs_delete_state(struct xfrm_state *x)
+{
+	struct xfrm_iptfs_data *xtfs = x->mode_data;
+
+	if (IS_ERR_OR_NULL(xtfs))
+		return;
+
+	spin_lock(&xtfs->drop_lock);
+	hrtimer_cancel(&xtfs->iptfs_timer);
+	hrtimer_cancel(&xtfs->drop_timer);
+	spin_unlock(&xtfs->drop_lock);
+
+	kfree_sensitive(xtfs->w_saved);
+	kfree_sensitive(xtfs);
+}
+
+static const struct xfrm_mode_cbs iptfs_mode_cbs = {
+	.owner = THIS_MODULE,
+	.create_state = iptfs_create_state,
+	.delete_state = iptfs_delete_state,
+	.user_init = iptfs_user_init,
+	.copy_to_user = iptfs_copy_to_user,
+	.get_inner_mtu = iptfs_get_inner_mtu,
+	.input = iptfs_input,
+	.output = iptfs_output_collect,
+	.prepare_output = iptfs_prepare_output,
+};
+
+static int __init xfrm_iptfs_init(void)
+{
+	int err;
+
+	pr_info("xfrm_iptfs: IPsec IP-TFS tunnel mode module\n");
+
+	err = xfrm_register_mode_cbs(XFRM_MODE_IPTFS, &iptfs_mode_cbs);
+	if (err < 0)
+		pr_info("%s: can't register IP-TFS\n", __func__);
+
+	return err;
+}
+
+static void __exit xfrm_iptfs_fini(void)
+{
+	xfrm_unregister_mode_cbs(XFRM_MODE_IPTFS);
+}
+
+module_init(xfrm_iptfs_init);
+module_exit(xfrm_iptfs_fini);
+MODULE_LICENSE("GPL");
