selftests/bpf: test for seg6local End.BPF action

Add a new test for the seg6local End.BPF action. The following helpers
are also tested:

- bpf_lwt_push_encap within the LWT BPF IN hook
- bpf_lwt_seg6_action
- bpf_lwt_seg6_adjust_srh
- bpf_lwt_seg6_store_bytes

A chain of End.BPF actions is built. The SRH is injected through a LWT
BPF IN hook before entering this chain. Each End.BPF action validates
the previous one, otherwise the packet is dropped. The test succeeds
if the last node in the chain receives the packet and the UDP datagram
contained can be retrieved from userspace.
Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/include/uapi/linux/bpf.h

@@ -141,6 +141,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_MSG,
 	BPF_PROG_TYPE_RAW_TRACEPOINT,
 	BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	BPF_PROG_TYPE_LWT_SEG6LOCAL,
 };
 
 enum bpf_attach_type {
@@ -1902,6 +1903,90 @@ union bpf_attr {
  *		egress otherwise). This is the only flag supported for now.
  *	Return
  *		**SK_PASS** on success, or **SK_DROP** on error.
+ *
+ * int bpf_lwt_push_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len)
+ *	Description
+ *		Encapsulate the packet associated to *skb* within a Layer 3
+ *		protocol header. This header is provided in the buffer at
+ *		address *hdr*, with *len* its size in bytes. *type* indicates
+ *		the protocol of the header and can be one of:
+ *
+ *		**BPF_LWT_ENCAP_SEG6**
+ *			IPv6 encapsulation with Segment Routing Header
+ *			(**struct ipv6_sr_hdr**). *hdr* only contains the SRH,
+ *			the IPv6 header is computed by the kernel.
+ *		**BPF_LWT_ENCAP_SEG6_INLINE**
+ *			Only works if *skb* contains an IPv6 packet. Insert a
+ *			Segment Routing Header (**struct ipv6_sr_hdr**) inside
+ *			the IPv6 header.
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_lwt_seg6_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len)
+ *	Description
+ *		Store *len* bytes from address *from* into the packet
+ *		associated to *skb*, at *offset*. Only the flags, tag and TLVs
+ *		inside the outermost IPv6 Segment Routing Header can be
+ *		modified through this helper.
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_lwt_seg6_adjust_srh(struct sk_buff *skb, u32 offset, s32 delta)
+ *	Description
+ *		Adjust the size allocated to TLVs in the outermost IPv6
+ *		Segment Routing Header contained in the packet associated to
+ *		*skb*, at position *offset* by *delta* bytes. Only offsets
+ *		after the segments are accepted. *delta* can be as well
+ *		positive (growing) as negative (shrinking).
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_lwt_seg6_action(struct sk_buff *skb, u32 action, void *param, u32 param_len)
+ *	Description
+ *		Apply an IPv6 Segment Routing action of type *action* to the
+ *		packet associated to *skb*. Each action takes a parameter
+ *		contained at address *param*, and of length *param_len* bytes.
+ *		*action* can be one of:
+ *
+ *		**SEG6_LOCAL_ACTION_END_X**
+ *			End.X action: Endpoint with Layer-3 cross-connect.
+ *			Type of *param*: **struct in6_addr**.
+ *		**SEG6_LOCAL_ACTION_END_T**
+ *			End.T action: Endpoint with specific IPv6 table lookup.
+ *			Type of *param*: **int**.
+ *		**SEG6_LOCAL_ACTION_END_B6**
+ *			End.B6 action: Endpoint bound to an SRv6 policy.
+ *			Type of param: **struct ipv6_sr_hdr**.
+ *		**SEG6_LOCAL_ACTION_END_B6_ENCAP**
+ *			End.B6.Encap action: Endpoint bound to an SRv6
+ *			encapsulation policy.
+ *			Type of param: **struct ipv6_sr_hdr**.
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -1976,7 +2061,11 @@ union bpf_attr {
 	FN(fib_lookup),			\
 	FN(sock_hash_update),		\
 	FN(msg_redirect_hash),		\
-	FN(sk_redirect_hash),
+	FN(sk_redirect_hash),		\
+	FN(lwt_push_encap),		\
+	FN(lwt_seg6_store_bytes),	\
+	FN(lwt_seg6_adjust_srh),	\
+	FN(lwt_seg6_action),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -2043,6 +2132,12 @@ enum bpf_hdr_start_off {
 	BPF_HDR_START_NET,
 };
 
+/* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
+enum bpf_lwt_encap_mode {
+	BPF_LWT_ENCAP_SEG6,
+	BPF_LWT_ENCAP_SEG6_INLINE
+};
+
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */

tools/testing/selftests/bpf/Makefile

@@ -33,7 +33,8 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
 	sample_map_ret0.o test_tcpbpf_kern.o test_stacktrace_build_id.o \
 	sockmap_tcp_msg_prog.o connect4_prog.o connect6_prog.o test_adjust_tail.o \
 	test_btf_haskv.o test_btf_nokv.o test_sockmap_kern.o test_tunnel_kern.o \
-	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o
+	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o \
+	test_lwt_seg6local.o
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \
@@ -42,7 +43,8 @@ TEST_PROGS := test_kmod.sh \
 	test_xdp_meta.sh \
 	test_offload.py \
 	test_sock_addr.sh \
-	test_tunnel.sh
+	test_tunnel.sh \
+	test_lwt_seg6local.sh
 
 # Compile but not part of 'make run_tests'
 TEST_GEN_PROGS_EXTENDED = test_libbpf_open test_sock_addr

tools/testing/selftests/bpf/bpf_helpers.h

@@ -114,6 +114,18 @@ static int (*bpf_get_stack)(void *ctx, void *buf, int size, int flags) =
 static int (*bpf_fib_lookup)(void *ctx, struct bpf_fib_lookup *params,
 			     int plen, __u32 flags) =
 	(void *) BPF_FUNC_fib_lookup;
+static int (*bpf_lwt_push_encap)(void *ctx, unsigned int type, void *hdr,
+				 unsigned int len) =
+	(void *) BPF_FUNC_lwt_push_encap;
+static int (*bpf_lwt_seg6_store_bytes)(void *ctx, unsigned int offset,
+				       void *from, unsigned int len) =
+	(void *) BPF_FUNC_lwt_seg6_store_bytes;
+static int (*bpf_lwt_seg6_action)(void *ctx, unsigned int action, void *param,
+				  unsigned int param_len) =
+	(void *) BPF_FUNC_lwt_seg6_action;
+static int (*bpf_lwt_seg6_adjust_srh)(void *ctx, unsigned int offset,
+				      unsigned int len) =
+	(void *) BPF_FUNC_lwt_seg6_adjust_srh;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions

tools/testing/selftests/bpf/test_lwt_seg6local.sh

+#!/bin/bash
+# Connects 6 network namespaces through veths.
+# Each NS may have different IPv6 global scope addresses :
+#   NS1 ---- NS2 ---- NS3 ---- NS4 ---- NS5 ---- NS6
+# fb00::1           fd00::1  fd00::2  fd00::3  fb00::6
+#                   fc42::1           fd00::4
+#
+# All IPv6 packets going to fb00::/16 through NS2 will be encapsulated in a
+# IPv6 header with a Segment Routing Header, with segments :
+# 	fd00::1 -> fd00::2 -> fd00::3 -> fd00::4
+#
+# 3 fd00::/16 IPv6 addresses are binded to seg6local End.BPF actions :
+# - fd00::1 : add a TLV, change the flags and apply a End.X action to fc42::1
+# - fd00::2 : remove the TLV, change the flags, add a tag
+# - fd00::3 : apply an End.T action to fd00::4, through routing table 117
+#
+# fd00::4 is a simple Segment Routing node decapsulating the inner IPv6 packet.
+# Each End.BPF action will validate the operations applied on the SRH by the
+# previous BPF program in the chain, otherwise the packet is dropped.
+#
+# An UDP datagram is sent from fb00::1 to fb00::6. The test succeeds if this
+# datagram can be read on NS6 when binding to fb00::6.
+
+TMP_FILE="/tmp/selftest_lwt_seg6local.txt"
+
+cleanup()
+{
+	if [ "$?" = "0" ]; then
+		echo "selftests: test_lwt_seg6local [PASS]";
+	else
+		echo "selftests: test_lwt_seg6local [FAILED]";
+	fi
+
+	set +e
+	ip netns del ns1 2> /dev/null
+	ip netns del ns2 2> /dev/null
+	ip netns del ns3 2> /dev/null
+	ip netns del ns4 2> /dev/null
+	ip netns del ns5 2> /dev/null
+	ip netns del ns6 2> /dev/null
+	rm -f $TMP_FILE
+}
+
+set -e
+
+ip netns add ns1
+ip netns add ns2
+ip netns add ns3
+ip netns add ns4
+ip netns add ns5
+ip netns add ns6
+
+trap cleanup 0 2 3 6 9
+
+ip link add veth1 type veth peer name veth2
+ip link add veth3 type veth peer name veth4
+ip link add veth5 type veth peer name veth6
+ip link add veth7 type veth peer name veth8
+ip link add veth9 type veth peer name veth10
+
+ip link set veth1 netns ns1
+ip link set veth2 netns ns2
+ip link set veth3 netns ns2
+ip link set veth4 netns ns3
+ip link set veth5 netns ns3
+ip link set veth6 netns ns4
+ip link set veth7 netns ns4
+ip link set veth8 netns ns5
+ip link set veth9 netns ns5
+ip link set veth10 netns ns6
+
+ip netns exec ns1 ip link set dev veth1 up
+ip netns exec ns2 ip link set dev veth2 up
+ip netns exec ns2 ip link set dev veth3 up
+ip netns exec ns3 ip link set dev veth4 up
+ip netns exec ns3 ip link set dev veth5 up
+ip netns exec ns4 ip link set dev veth6 up
+ip netns exec ns4 ip link set dev veth7 up
+ip netns exec ns5 ip link set dev veth8 up
+ip netns exec ns5 ip link set dev veth9 up
+ip netns exec ns6 ip link set dev veth10 up
+ip netns exec ns6 ip link set dev lo up
+
+# All link scope addresses and routes required between veths
+ip netns exec ns1 ip -6 addr add fb00::12/16 dev veth1 scope link
+ip netns exec ns1 ip -6 route add fb00::21 dev veth1 scope link
+ip netns exec ns2 ip -6 addr add fb00::21/16 dev veth2 scope link
+ip netns exec ns2 ip -6 addr add fb00::34/16 dev veth3 scope link
+ip netns exec ns2 ip -6 route add fb00::43 dev veth3 scope link
+ip netns exec ns3 ip -6 route add fb00::65 dev veth5 scope link
+ip netns exec ns3 ip -6 addr add fb00::43/16 dev veth4 scope link
+ip netns exec ns3 ip -6 addr add fb00::56/16 dev veth5 scope link
+ip netns exec ns4 ip -6 addr add fb00::65/16 dev veth6 scope link
+ip netns exec ns4 ip -6 addr add fb00::78/16 dev veth7 scope link
+ip netns exec ns4 ip -6 route add fb00::87 dev veth7 scope link
+ip netns exec ns5 ip -6 addr add fb00::87/16 dev veth8 scope link
+ip netns exec ns5 ip -6 addr add fb00::910/16 dev veth9 scope link
+ip netns exec ns5 ip -6 route add fb00::109 dev veth9 scope link
+ip netns exec ns5 ip -6 route add fb00::109 table 117 dev veth9 scope link
+ip netns exec ns6 ip -6 addr add fb00::109/16 dev veth10 scope link
+
+ip netns exec ns1 ip -6 addr add fb00::1/16 dev lo
+ip netns exec ns1 ip -6 route add fb00::6 dev veth1 via fb00::21
+
+ip netns exec ns2 ip -6 route add fb00::6 encap bpf in obj test_lwt_seg6local.o sec encap_srh dev veth2
+ip netns exec ns2 ip -6 route add fd00::1 dev veth3 via fb00::43 scope link
+
+ip netns exec ns3 ip -6 route add fc42::1 dev veth5 via fb00::65
+ip netns exec ns3 ip -6 route add fd00::1 encap seg6local action End.BPF obj test_lwt_seg6local.o sec add_egr_x dev veth4
+
+ip netns exec ns4 ip -6 route add fd00::2 encap seg6local action End.BPF obj test_lwt_seg6local.o sec pop_egr dev veth6
+ip netns exec ns4 ip -6 addr add fc42::1 dev lo
+ip netns exec ns4 ip -6 route add fd00::3 dev veth7 via fb00::87
+
+ip netns exec ns5 ip -6 route add fd00::4 table 117 dev veth9 via fb00::109
+ip netns exec ns5 ip -6 route add fd00::3 encap seg6local action End.BPF obj test_lwt_seg6local.o sec inspect_t dev veth8
+
+ip netns exec ns6 ip -6 addr add fb00::6/16 dev lo
+ip netns exec ns6 ip -6 addr add fd00::4/16 dev lo
+
+ip netns exec ns1 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns2 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns3 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns4 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns5 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+
+ip netns exec ns6 sysctl net.ipv6.conf.all.seg6_enabled=1 > /dev/null
+ip netns exec ns6 sysctl net.ipv6.conf.lo.seg6_enabled=1 > /dev/null
+ip netns exec ns6 sysctl net.ipv6.conf.veth10.seg6_enabled=1 > /dev/null
+
+ip netns exec ns6 nc -l -6 -u -d 7330 > $TMP_FILE &
+ip netns exec ns1 bash -c "echo 'foobar' | nc -w0 -6 -u -p 2121 -s fb00::1 fb00::6 7330"
+sleep 5 # wait enough time to ensure the UDP datagram arrived to the last segment
+kill -INT $!
+
+if [[ $(< $TMP_FILE) != "foobar" ]]; then
+	exit 1
+fi
+
+exit 0