diff mbox series

[v10,bpf-next,10/18] bpf: add multi-buff support to the bpf_xdp_adjust_tail() API

Message ID b6344a2548ab1c2860de4a0a84a4b74572e0b30d.1627463617.git.lorenzo@kernel.org (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series mvneta: introduce XDP multi-buffer support | expand

Checks

Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count fail Series longer than 15 patches
netdev/tree_selection success Clearly marked for bpf-next
netdev/subject_prefix success Link
netdev/cc_maintainers warning 6 maintainers not CCed: yhs@fb.com kpsingh@kernel.org hawk@kernel.org andrii@kernel.org kafai@fb.com songliubraving@fb.com
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 4765 this patch: 4765
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 109 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 4828 this patch: 4828
netdev/header_inline success Link

Commit Message

Lorenzo Bianconi July 28, 2021, 9:38 a.m. UTC 
From: Eelco Chaudron <echaudro@redhat.com>

This change adds support for tail growing and shrinking for XDP multi-buff.

When called on a multi-buffer packet with a grow request, it will always
work on the last fragment of the packet. So the maximum grow size is the
last fragments tailroom, i.e. no new buffer will be allocated.

When shrinking, it will work from the last fragment, all the way down to
the base buffer depending on the shrinking size. It's important to mention
that once you shrink down the fragment(s) are freed, so you can not grow
again to the original size.

Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
 include/net/xdp.h |  9 +++++++
 net/core/filter.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++
 net/core/xdp.c    |  5 ++--
 3 files changed, 72 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/include/net/xdp.h b/include/net/xdp.h
index d66e9877d773..cdaecf8d4d61 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -145,6 +145,13 @@  xdp_get_shared_info_from_buff(struct xdp_buff *xdp)
 	return (struct skb_shared_info *)xdp_data_hard_end(xdp);
 }
 
+static inline unsigned int xdp_get_frag_tailroom(const skb_frag_t *frag)
+{
+	struct page *page = skb_frag_page(frag);
+
+	return page_size(page) - skb_frag_size(frag) - skb_frag_off(frag);
+}
+
 struct xdp_frame {
 	void *data;
 	u16 len;
@@ -290,6 +297,8 @@  struct xdp_frame *xdp_convert_buff_to_frame(struct xdp_buff *xdp)
 	return xdp_frame;
 }
 
+void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
+		  struct xdp_buff *xdp);
 void xdp_return_frame(struct xdp_frame *xdpf);
 void xdp_return_frame_rx_napi(struct xdp_frame *xdpf);
 void xdp_return_buff(struct xdp_buff *xdp);
diff --git a/net/core/filter.c b/net/core/filter.c
index faf29fd82276..e60e300b10cd 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3835,11 +3835,71 @@  static const struct bpf_func_proto bpf_xdp_adjust_head_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+static int bpf_xdp_mb_adjust_tail(struct xdp_buff *xdp, int offset)
+{
+	struct skb_shared_info *sinfo;
+
+	sinfo = xdp_get_shared_info_from_buff(xdp);
+	if (offset >= 0) {
+		skb_frag_t *frag = &sinfo->frags[sinfo->nr_frags - 1];
+		int size;
+
+		if (unlikely(offset > xdp_get_frag_tailroom(frag)))
+			return -EINVAL;
+
+		size = skb_frag_size(frag);
+		memset(skb_frag_address(frag) + size, 0, offset);
+		skb_frag_size_set(frag, size + offset);
+		sinfo->xdp_frags_size += offset;
+	} else {
+		int i, n_frags_free = 0, len_free = 0, tlen_free = 0;
+
+		offset = abs(offset);
+		if (unlikely(offset > ((int)(xdp->data_end - xdp->data) +
+				       sinfo->xdp_frags_size - ETH_HLEN)))
+			return -EINVAL;
+
+		for (i = sinfo->nr_frags - 1; i >= 0 && offset > 0; i--) {
+			skb_frag_t *frag = &sinfo->frags[i];
+			int size = skb_frag_size(frag);
+			int shrink = min_t(int, offset, size);
+
+			len_free += shrink;
+			offset -= shrink;
+
+			if (unlikely(size == shrink)) {
+				struct page *page = skb_frag_page(frag);
+
+				__xdp_return(page_address(page), &xdp->rxq->mem,
+					     false, NULL);
+				tlen_free += page_size(page);
+				n_frags_free++;
+			} else {
+				skb_frag_size_set(frag, size - shrink);
+				break;
+			}
+		}
+		sinfo->nr_frags -= n_frags_free;
+		sinfo->xdp_frags_size -= len_free;
+		sinfo->xdp_frags_tsize -= tlen_free;
+
+		if (unlikely(offset > 0)) {
+			xdp_buff_clear_mb(xdp);
+			xdp->data_end -= offset;
+		}
+	}
+
+	return 0;
+}
+
 BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
 {
 	void *data_hard_end = xdp_data_hard_end(xdp); /* use xdp->frame_sz */
 	void *data_end = xdp->data_end + offset;
 
+	if (unlikely(xdp_buff_is_mb(xdp)))
+		return bpf_xdp_mb_adjust_tail(xdp, offset);
+
 	/* Notice that xdp_data_hard_end have reserved some tailroom */
 	if (unlikely(data_end > data_hard_end))
 		return -EINVAL;
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 1346fb8b3f50..a71cdea75306 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -339,8 +339,8 @@  EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);
  * is used for those calls sites.  Thus, allowing for faster recycling
  * of xdp_frames/pages in those cases.
  */
-static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
-			 struct xdp_buff *xdp)
+void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
+		  struct xdp_buff *xdp)
 {
 	struct xdp_mem_allocator *xa;
 	struct page *page;
@@ -373,6 +373,7 @@  static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
 		break;
 	}
 }
+EXPORT_SYMBOL_GPL(__xdp_return);
 
 void xdp_return_frame(struct xdp_frame *xdpf)
 {