[bpf-next,2/3] bpf,fou: Add bpf_skb_{set,get}_fou_encap kfuncs

Commit Message

Christian Ehrig April 1, 2023, 8:33 p.m. UTC

Add two new kfuncs that allow a BPF tc-hook, installed on an ipip
device in collect-metadata mode, to control FOU encap parameters on a
per-packet level. The set of kfuncs is registered with the fou module.

The bpf_skb_set_fou_encap kfunc is supposed to be used in tandem and after
a successful call to the bpf_skb_set_tunnel_key bpf-helper. UDP source and
destination ports can be controlled by passing a struct bpf_fou_encap. A
source port of zero will auto-assign a source port. enum bpf_fou_encap_type
is used to specify if the egress path should FOU or GUE encap the packet.

On the ingress path bpf_skb_get_fou_encap can be used to read UDP source
and destination ports from the receiver's point of view and allows for
packet multiplexing across different destination ports within a single
BPF program and ipip device.

Signed-off-by: Christian Ehrig <[e-mail]>
---
 include/net/fou.h   |   2 +
 net/ipv4/Makefile   |   2 +-
 net/ipv4/fou_bpf.c  | 118 ++++++++++++++++++++++++++++++++++++++++++++
 net/ipv4/fou_core.c |   5 ++
 4 files changed, 126 insertions(+), 1 deletion(-)
 create mode 100644 net/ipv4/fou_bpf.c

Comments

kernel test robot April 1, 2023, 8:51 p.m. UTC | #1

Hi Christian,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Christian-Ehrig/ipip-ip_tunnel-sit-Add-FOU-support-for-externally-controlled-ipip-devices/20230402-033512
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/65b05e447b28d32fb0e07275dc988989f358da2c.1680379518.git.cehrig%40cloudflare.com
patch subject: [PATCH bpf-next 2/3] bpf,fou: Add bpf_skb_{set,get}_fou_encap kfuncs
config: microblaze-randconfig-r021-20230402 (https://download.01.org/0day-ci/archive/20230402/[e-mail]/config)
compiler: microblaze-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/111ef54093a724110ca63e6a6279e60dd669094b
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Christian-Ehrig/ipip-ip_tunnel-sit-Add-FOU-support-for-externally-controlled-ipip-devices/20230402-033512
        git checkout 111ef54093a724110ca63e6a6279e60dd669094b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=microblaze olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=microblaze SHELL=/bin/bash net/ipv4/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[e-mail]>
| Link: https://lore.kernel.org/oe-kbuild-all/[e-mail]/

All warnings (new ones prefixed by >>):

>> net/ipv4/fou_bpf.c:114:5: warning: no previous prototype for 'register_fou_bpf' [-Wmissing-prototypes]
     114 | int register_fou_bpf(void)
         |     ^~~~~~~~~~~~~~~~


vim +/register_fou_bpf +114 net/ipv4/fou_bpf.c

   113	
 > 114	int register_fou_bpf(void)

kernel test robot April 1, 2023, 8:51 p.m. UTC | #2

Hi Christian,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Christian-Ehrig/ipip-ip_tunnel-sit-Add-FOU-support-for-externally-controlled-ipip-devices/20230402-033512
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/65b05e447b28d32fb0e07275dc988989f358da2c.1680379518.git.cehrig%40cloudflare.com
patch subject: [PATCH bpf-next 2/3] bpf,fou: Add bpf_skb_{set,get}_fou_encap kfuncs
config: i386-randconfig-a005 (https://download.01.org/0day-ci/archive/20230402/[e-mail]/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/111ef54093a724110ca63e6a6279e60dd669094b
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Christian-Ehrig/ipip-ip_tunnel-sit-Add-FOU-support-for-externally-controlled-ipip-devices/20230402-033512
        git checkout 111ef54093a724110ca63e6a6279e60dd669094b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash net/ipv4/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[e-mail]>
| Link: https://lore.kernel.org/oe-kbuild-all/[e-mail]/

All warnings (new ones prefixed by >>):

>> net/ipv4/fou_bpf.c:114:5: warning: no previous prototype for 'register_fou_bpf' [-Wmissing-prototypes]
     114 | int register_fou_bpf(void)
         |     ^~~~~~~~~~~~~~~~


vim +/register_fou_bpf +114 net/ipv4/fou_bpf.c

   113	
 > 114	int register_fou_bpf(void)

Patch

diff --git a/include/net/fou.h b/include/net/fou.h
index 80f56e275b08..824eb4b231fd 100644
--- a/include/net/fou.h
+++ b/include/net/fou.h
@@ -17,4 +17,6 @@  int __fou_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e,
 int __gue_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e,
 		       u8 *protocol, __be16 *sport, int type);
 
+int register_fou_bpf(void);
+
 #endif
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 880277c9fd07..b18ba8ef93ad 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -26,7 +26,7 @@  obj-$(CONFIG_IP_MROUTE) += ipmr.o
 obj-$(CONFIG_IP_MROUTE_COMMON) += ipmr_base.o
 obj-$(CONFIG_NET_IPIP) += ipip.o
 gre-y := gre_demux.o
-fou-y := fou_core.o fou_nl.o
+fou-y := fou_core.o fou_nl.o fou_bpf.o
 obj-$(CONFIG_NET_FOU) += fou.o
 obj-$(CONFIG_NET_IPGRE_DEMUX) += gre.o
 obj-$(CONFIG_NET_IPGRE) += ip_gre.o
diff --git a/net/ipv4/fou_bpf.c b/net/ipv4/fou_bpf.c
new file mode 100644
index 000000000000..462298d87a2f
--- /dev/null
+++ b/net/ipv4/fou_bpf.c
@@ -0,0 +1,118 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Unstable Fou Helpers for TC-BPF hook
+ *
+ * These are called from SCHED_CLS BPF programs. Note that it is
+ * allowed to break compatibility for these functions since the interface they
+ * are exposed through to BPF programs is explicitly unstable.
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf_ids.h>
+
+#include <net/dst_metadata.h>
+
+struct bpf_fou_encap {
+	__be16 sport;
+	__be16 dport;
+};
+
+enum bpf_fou_encap_type {
+	FOU_BPF_ENCAP_FOU,
+	FOU_BPF_ENCAP_GUE,
+};
+
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "Global functions as their definitions will be in BTF");
+
+/* bpf_skb_set_fou_encap - Set FOU encap parameters
+ *
+ * This function allows for using GUE or FOU encapsulation together with an
+ * ipip device in collect-metadata mode.
+ *
+ * It is meant to be used in BPF tc-hooks and after a call to the
+ * bpf_skb_set_tunnel_key helper, responsible for setting IP addresses.
+ *
+ * Parameters:
+ * @skb_ctx	Pointer to ctx (__sk_buff) in TC program. Cannot be NULL
+ * @encap	Pointer to a `struct bpf_fou_encap` storing UDP src and
+ * 		dst ports. If sport is set to 0 the kernel will auto-assign a
+ * 		port. This is similar to using `encap-sport auto`.
+ * 		Cannot be NULL
+ * @type	Encapsulation type for the packet. Their definitions are
+ * 		specified in `enum bpf_fou_encap_type`
+ */
+__bpf_kfunc int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx,
+				      struct bpf_fou_encap *encap, int type)
+{
+	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+	struct ip_tunnel_info *info = skb_tunnel_info(skb);
+
+	if (unlikely(!encap))
+		return -EINVAL;
+
+	if (unlikely(!info || !(info->mode & IP_TUNNEL_INFO_TX)))
+		return -EINVAL;
+
+	switch (type) {
+	case FOU_BPF_ENCAP_FOU:
+		info->encap.type = TUNNEL_ENCAP_FOU;
+		break;
+	case FOU_BPF_ENCAP_GUE:
+		info->encap.type = TUNNEL_ENCAP_GUE;
+		break;
+	default:
+		info->encap.type = TUNNEL_ENCAP_NONE;
+	}
+
+	if (info->key.tun_flags & TUNNEL_CSUM)
+		info->encap.flags |= TUNNEL_ENCAP_FLAG_CSUM;
+
+	info->encap.sport = encap->sport;
+	info->encap.dport = encap->dport;
+
+	return 0;
+}
+
+/* bpf_skb_get_fou_encap - Get FOU encap parameters
+ *
+ * This function allows for reading encap metadata from a packet received
+ * on an ipip device in collect-metadata mode.
+ *
+ * Parameters:
+ * @skb_ctx	Pointer to ctx (__sk_buff) in TC program. Cannot be NULL
+ * @encap	Pointer to a struct bpf_fou_encap storing UDP source and
+ * 		destination port. Cannot be NULL
+ */
+__bpf_kfunc int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
+				      struct bpf_fou_encap *encap)
+{
+	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+	struct ip_tunnel_info *info = skb_tunnel_info(skb);
+
+	if (unlikely(!info))
+		return -EINVAL;
+
+	encap->sport = info->encap.sport;
+	encap->dport = info->encap.dport;
+
+	return 0;
+}
+
+__diag_pop()
+
+BTF_SET8_START(fou_kfunc_set)
+BTF_ID_FLAGS(func, bpf_skb_set_fou_encap)
+BTF_ID_FLAGS(func, bpf_skb_get_fou_encap)
+BTF_SET8_END(fou_kfunc_set)
+
+static const struct btf_kfunc_id_set fou_bpf_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &fou_kfunc_set,
+};
+
+int register_fou_bpf(void)
+{
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
+					 &fou_bpf_kfunc_set);
+}
diff --git a/net/ipv4/fou_core.c b/net/ipv4/fou_core.c
index cafec9b4eee0..0c41076e31ed 100644
--- a/net/ipv4/fou_core.c
+++ b/net/ipv4/fou_core.c
@@ -1236,10 +1236,15 @@  static int __init fou_init(void)
 	if (ret < 0)
 		goto unregister;
 
+	ret = register_fou_bpf();
+	if (ret < 0)
+		goto kfunc_failed;
+
 	ret = ip_tunnel_encap_add_fou_ops();
 	if (ret == 0)
 		return 0;
 
+kfunc_failed:
 	genl_unregister_family(&fou_nl_family);
 unregister:
 	unregister_pernet_device(&fou_net_ops);