[PATCH bpf-next v8 0/7] bpf: add icmp_send kfunc

[PATCH bpf-next v8 0/7] bpf: add icmp_send kfunc

[Mahe Tardy]

Hello,

This is v8 of adding the icmp_send kfunc, as suggested during LSF/MM/BPF
2025[^1]. The goal is to allow cgroup_skb programs to actively reject
east-west traffic, similarly to what is possible to do with netfilter
reject target. Applications can receive early feedback that something
went wrong during the TCP handshake.

The first step to implement this is using ICMP control messages, with
the ICMP_DEST_UNREACH type with various code ICMP_NET_UNREACH,
ICMP_HOST_UNREACH, ICMP_PROT_UNREACH, etc. This is easier to implement
than a TCP RST reply and will already hint the client TCP stack to abort
the connection and not retry extensively.

Note that this is different than the sock_destroy kfunc, that along
calls tcp_abort and thus sends a reset, destroying the underlying
socket.

Caveats of this kfunc design are that a program can call this function N
times, thus send N ICMP unreach control messages and that the program
can return from the BPF filter with pass leading to a potential
confusing situation where the TCP connection was established while the
client received ICMP_DEST_UNREACH messages.

v2 updates:
- fix a build error from a missing function call rename;
- avoid changing return line in bpf_kfunc_init;
- return SK_DROP from the kfunc (similarly to bpf_redirect);
- check the return value in the selftest.

v3 update:
- fix an undefined reference build error.

v4 updates:
- prevent the kfunc to be called recursively and add a test (thanks to
  Martin).
- do not fetch dst route when unnecessary (thanks to Martin).
- extend the test for IPv6 (thanks to Martin).
- use SK_DROP in examples and use non blocking sockets for testing
  (thanks to Martin).
- test when the kfunc returns -EINVAL (thanks to Jordan).
- add the kfunc to bpf_kfunc_set_skb as suggested by Alexei.
- guard the IPv4 parts with IS_ENABLED(CONFIG_INET).
- fix a wrong initial value for client_fd (thanks to Yonghong).
- add documentation to the kfunc.
- to Jordan: I couldn't include <linux/icmp.h> because of redefines from
  <network_helpers.h>.

v5 updates:
- kfunc name is now icmp_send and takes the control message type as
  parameter for future potential extension (daniel)
- drop the net patches to route packet since now the kfunc is limited to
  cgroup_skb and tc progs (daniel & martin)
- linearize skb headers (sashiko)
- zero SKB control block (sashiko)
- bind to port 0 instead of fixed port (sashiko)
- poll to wait for POLLERR event (sashiko)
- do not use ASSERT_EQ in CMSG_NXTHDR loop (sashiko)
- fix comment about byte order (sashiko)
- fix endianness IP address issue (sashiko)
- add forgotten cleanup_cgroup_environment (sashiko)
- let packets pass in recursion test (sashiko)
- clarify evaluation order for recursion test (sashiko)

v6 updates (all from sashiko):
- bring back the net patches to route packet since tc ingress needs it.
- rename the ip_route_reply helpers from fetch to fill.
- call pskb_network_may_pull on the cloned pkt.
- check explicitly that we received one and only one ICMP err ctrl msg.

v7 updates:
- use consume_skb on success path (stanislav)
- replace recursion protection with CPU_ARRAY by checking the nature of
  the sk (daniel, offline)
- use reverse xmas tree in read_icmp_errqueue (jordan)
- use ASSERT_OK_FD instead of ASSERT_GE whenever possible (jordan)
- add a test for tc (jordan)
- better filtering from host cgroup test progs (sashiko)

v8 updates:
- mostly a resend as it's been sitting as "New" in the queue for almost
  one month, fixed a few nits.
- on new bpf_icmp_send kfunc cgroup_skb test (patch 4/7):
  - guard a close fd with fd >= 0 (jordan)
  - use ASSERT_OK_FD instead of ASSERT_GE (jordan)
  - fixed comment style (sashiko)
- on recursion test (patch 7/7):
  - guard a close fd with fd >= 0 (jordan)
  - fixed comments style (sashiko)
  - filter bpf prog on pid and ICMP message types (sashiko)

[^1]: https://lwn.net/Articles/1022034/

Link to v7: https://lore.kernel.org/bpf/20260526153708.279717-1-mahe.tardy@gmail.com/

Mahe Tardy (7):
  net: move netfilter nf_reject_fill_skb_dst to core ipv4
  net: move netfilter nf_reject6_fill_skb_dst to core ipv6
  bpf: add bpf_icmp_send kfunc
  selftests/bpf: add bpf_icmp_send kfunc cgroup_skb tests
  selftests/bpf: add bpf_icmp_send kfunc cgroup_skb IPv6 tests
  selftests/bpf: add bpf_icmp_send kfunc tc tests
  selftests/bpf: add bpf_icmp_send recursion test

 include/net/ip6_route.h                       |   2 +
 include/net/route.h                           |   1 +
 net/core/filter.c                             | 109 ++++++++
 net/ipv4/netfilter/nf_reject_ipv4.c           |  19 +-
 net/ipv4/route.c                              |  15 ++
 net/ipv6/netfilter/nf_reject_ipv6.c           |  17 +-
 net/ipv6/route.c                              |  18 ++
 .../bpf/prog_tests/icmp_send_kfunc.c          | 248 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/icmp_send.c | 184 +++++++++++++
 9 files changed, 580 insertions(+), 33 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/progs/icmp_send.c

--
2.34.1


Mahe Tardy (7):
  net: move netfilter nf_reject_fill_skb_dst to core ipv4
  net: move netfilter nf_reject6_fill_skb_dst to core ipv6
  bpf: add bpf_icmp_send kfunc
  selftests/bpf: add bpf_icmp_send kfunc cgroup_skb tests
  selftests/bpf: add bpf_icmp_send kfunc cgroup_skb IPv6 tests
  selftests/bpf: add bpf_icmp_send kfunc tc tests
  selftests/bpf: add bpf_icmp_send recursion test

 include/net/ip6_route.h                       |   2 +
 include/net/route.h                           |   1 +
 net/core/filter.c                             | 109 ++++++++
 net/ipv4/netfilter/nf_reject_ipv4.c           |  19 +-
 net/ipv4/route.c                              |  15 ++
 net/ipv6/netfilter/nf_reject_ipv6.c           |  17 +-
 net/ipv6/route.c                              |  18 ++
 .../bpf/prog_tests/icmp_send_kfunc.c          | 250 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/icmp_send.c | 184 +++++++++++++
 9 files changed, 582 insertions(+), 33 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/progs/icmp_send.c

--
2.34.1

[PATCH bpf-next v8 1/7] net: move netfilter nf_reject_fill_skb_dst to core ipv4

[Mahe Tardy]

Move and rename nf_reject_fill_skb_dst from
ipv4/netfilter/nf_reject_ipv4 to ip_route_reply_fill_dst in ipv4/route.c
so that it can be reused in the following patches by BPF kfuncs.

Netfilter uses nf_ip_route that is almost a transparent wrapper around
ip_route_output_key so this patch inlines it.

Reviewed-by: Jordan Rife <jordan@jrife.io>
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 include/net/route.h                 |  1 +
 net/ipv4/netfilter/nf_reject_ipv4.c | 19 ++-----------------
 net/ipv4/route.c                    | 15 +++++++++++++++
 3 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/include/net/route.h b/include/net/route.h
index f90106f383c5..300d292cd9a1 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -173,6 +173,7 @@ struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,
 				    const struct sock *sk);
 struct dst_entry *ipv4_blackhole_route(struct net *net,
 				       struct dst_entry *dst_orig);
+int ip_route_reply_fill_dst(struct sk_buff *skb);

 static inline struct rtable *ip_route_output_key(struct net *net, struct flowi4 *flp)
 {
diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index fecf6621f679..c1c0724e4d4d 100644
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -252,21 +252,6 @@ static void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *
 	nskb->csum_offset = offsetof(struct tcphdr, check);
 }

-static int nf_reject_fill_skb_dst(struct sk_buff *skb_in)
-{
-	struct dst_entry *dst = NULL;
-	struct flowi fl;
-
-	memset(&fl, 0, sizeof(struct flowi));
-	fl.u.ip4.daddr = ip_hdr(skb_in)->saddr;
-	nf_ip_route(dev_net(skb_in->dev), &dst, &fl, false);
-	if (!dst)
-		return -1;
-
-	skb_dst_set(skb_in, dst);
-	return 0;
-}
-
 /* Send RST reply */
 void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
 		   int hook)
@@ -279,7 +264,7 @@ void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
 	if (!oth)
 		return;

-	if (!skb_dst(oldskb) && nf_reject_fill_skb_dst(oldskb) < 0)
+	if (!skb_dst(oldskb) && ip_route_reply_fill_dst(oldskb) < 0)
 		return;

 	if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
@@ -352,7 +337,7 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook)
 	if (iph->frag_off & htons(IP_OFFSET))
 		return;

-	if (!skb_dst(skb_in) && nf_reject_fill_skb_dst(skb_in) < 0)
+	if (!skb_dst(skb_in) && ip_route_reply_fill_dst(skb_in) < 0)
 		return;

 	if (skb_csum_unnecessary(skb_in) ||
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 3f3de5164d6e..f24609933fbe 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2942,6 +2942,21 @@ struct rtable *ip_route_output_flow(struct net *net, struct flowi4 *flp4,
 }
 EXPORT_SYMBOL_GPL(ip_route_output_flow);

+int ip_route_reply_fill_dst(struct sk_buff *skb)
+{
+	struct rtable *rt;
+	struct flowi4 fl4 = {
+		.daddr = ip_hdr(skb)->saddr
+	};
+
+	rt = ip_route_output_key(dev_net(skb->dev), &fl4);
+	if (IS_ERR(rt))
+		return PTR_ERR(rt);
+	skb_dst_set(skb, &rt->dst);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ip_route_reply_fill_dst);
+
 /* called with rcu_read_lock held */
 static int rt_fill_info(struct net *net, __be32 dst, __be32 src,
 			struct rtable *rt, u32 table_id, dscp_t dscp,
--
2.34.1

[PATCH bpf-next v8 2/7] net: move netfilter nf_reject6_fill_skb_dst to core ipv6

[Mahe Tardy]

Move and rename nf_reject6_fill_skb_dst from
ipv6/netfilter/nf_reject_ipv6 to ip6_route_reply_fill_dst in
ipv6/route.c so that it can be reused in the following patches by BPF
kfuncs.

Netfilter uses nf_ip6_route that is almost a transparent wrapper around
ip6_route_output so this patch inlines it.

Reviewed-by: Jordan Rife <jordan@jrife.io>
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 include/net/ip6_route.h             |  2 ++
 net/ipv6/netfilter/nf_reject_ipv6.c | 17 +----------------
 net/ipv6/route.c                    | 18 ++++++++++++++++++
 3 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 09ffe0f13ce7..eb5a60d3babe 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -100,6 +100,8 @@ static inline struct dst_entry *ip6_route_output(struct net *net,
 	return ip6_route_output_flags(net, sk, fl6, 0);
 }

+int ip6_route_reply_fill_dst(struct sk_buff *skb);
+
 /* Only conditionally release dst if flags indicates
  * !RT6_LOOKUP_F_DST_NOREF or dst is in uncached_list.
  */
diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c
index ef5b7e85cffa..7d2f577e72b8 100644
--- a/net/ipv6/netfilter/nf_reject_ipv6.c
+++ b/net/ipv6/netfilter/nf_reject_ipv6.c
@@ -293,21 +293,6 @@ nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
 						   sizeof(struct tcphdr), 0));
 }

-static int nf_reject6_fill_skb_dst(struct sk_buff *skb_in)
-{
-	struct dst_entry *dst = NULL;
-	struct flowi fl;
-
-	memset(&fl, 0, sizeof(struct flowi));
-	fl.u.ip6.daddr = ipv6_hdr(skb_in)->saddr;
-	nf_ip6_route(dev_net(skb_in->dev), &dst, &fl, false);
-	if (!dst)
-		return -1;
-
-	skb_dst_set(skb_in, dst);
-	return 0;
-}
-
 void nf_send_reset6(struct net *net, struct sock *sk, struct sk_buff *oldskb,
 		    int hook)
 {
@@ -440,7 +425,7 @@ void nf_send_unreach6(struct net *net, struct sk_buff *skb_in,
 	if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
 		skb_in->dev = net->loopback_dev;

-	if (!skb_dst(skb_in) && nf_reject6_fill_skb_dst(skb_in) < 0)
+	if (!skb_dst(skb_in) && ip6_route_reply_fill_dst(skb_in) < 0)
 		return;

 	icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 6361ad2fcf77..0fa56c801178 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2732,6 +2732,24 @@ struct dst_entry *ip6_route_output_flags(struct net *net,
 }
 EXPORT_SYMBOL_GPL(ip6_route_output_flags);

+int ip6_route_reply_fill_dst(struct sk_buff *skb)
+{
+	struct dst_entry *result;
+	struct flowi6 fl = {
+		.daddr = ipv6_hdr(skb)->saddr
+	};
+	int err;
+
+	result = ip6_route_output(dev_net(skb->dev), NULL, &fl);
+	err = result->error;
+	if (err)
+		dst_release(result);
+	else
+		skb_dst_set(skb, result);
+	return err;
+}
+EXPORT_SYMBOL_GPL(ip6_route_reply_fill_dst);
+
 struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_orig)
 {
 	struct rt6_info *rt, *ort = dst_rt6_info(dst_orig);
--
2.34.1

[PATCH bpf-next v8 3/7] bpf: add bpf_icmp_send kfunc

[Mahe Tardy]

This is needed in the context of Tetragon to provide improved feedback
(in contrast to just dropping packets) to east-west traffic when blocked
by policies using cgroup_skb programs. We also extend this kfunc to tc
program as a convenience.

This reuses concepts from netfilter reject target codepath with the
differences that:
* Packets are cloned since the BPF user can still let the packet pass
  (SK_PASS from the cgroup_skb progs for example) and the current skb
  need to stay untouched (cgroup_skb hooks only allow read-only skb
  payload).
* We protect against recursion since the kfunc, by generating an ICMP
  error message, could retrigger the BPF prog that invoked it.

For now, we support cgroup_skb and tc program types. For cgroup_skb and
tc egress, almost everything should be good. However for tc ingress:
- packet will not be routed yet: need to set the net device for
  icmp_send, thus the call to ip[6]_route_reply_fill_dst.
- fragments could trigger hook: icmp_send will only reply to fragment 0.
- ensure the ip headers is linearized before processing, and zero out
  the SKB control block after cloning to prevent icmp_send()/icmpv6_send()
  from misinterpreting garbage data as IP options.

Only ICMP_DEST_UNREACH and ICMPV6_DEST_UNREACH are currently supported.
The interface accepts a type parameter to facilitate future extension to
other ICMP control message types.

Reviewed-by: Jordan Rife <jordan@jrife.io>
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 net/core/filter.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 2e96b4b847ce..fc69a14650e4 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -84,6 +84,8 @@
 #include <linux/un.h>
 #include <net/xdp_sock_drv.h>
 #include <net/inet_dscp.h>
+#include <linux/icmpv6.h>
+#include <net/icmp.h>

 #include "dev.h"

@@ -12546,6 +12548,101 @@ __bpf_kfunc int bpf_xdp_pull_data(struct xdp_md *x, u32 len)
 	return 0;
 }

+/**
+ * bpf_icmp_send - Send an ICMP control message
+ * @skb_ctx: Packet that triggered the control message
+ * @type: ICMP type (only ICMP_DEST_UNREACH/ICMPV6_DEST_UNREACH supported)
+ * @code: ICMP code (0-15 for IPv4, 0-6 for IPv6)
+ *
+ * Sends an ICMP control message in response to the packet. The original packet
+ * is cloned before sending the ICMP message, so the BPF program can still let
+ * the packet pass if desired.
+ *
+ * Currently only ICMP_DEST_UNREACH (IPv4) and ICMPV6_DEST_UNREACH (IPv6) are
+ * supported.
+ *
+ * Return: 0 on success, negative error code on failure:
+ *         -EINVAL: Invalid code parameter
+ *         -EBADMSG: Packet too short or malformed
+ *         -ENOMEM: Memory allocation failed
+ *         -EBUSY: Recursion detected
+ *         -EHOSTUNREACH: Routing failed
+ *         -EPROTONOSUPPORT: Non-IP protocol
+ *         -EOPNOTSUPP: Unsupported ICMP type
+ */
+__bpf_kfunc int bpf_icmp_send(struct __sk_buff *skb_ctx, int type, int code)
+{
+	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+	struct sk_buff *nskb;
+	struct sock *sk;
+
+	sk = skb_to_full_sk(skb);
+	if (sk && sk->sk_kern_sock &&
+	    (sk->sk_protocol == IPPROTO_ICMP || sk->sk_protocol == IPPROTO_ICMPV6))
+		return -EBUSY;
+
+	switch (skb->protocol) {
+#if IS_ENABLED(CONFIG_INET)
+	case htons(ETH_P_IP):
+		if (type != ICMP_DEST_UNREACH)
+			return -EOPNOTSUPP;
+		if (code < 0 || code > NR_ICMP_UNREACH)
+			return -EINVAL;
+
+		nskb = skb_clone(skb, GFP_ATOMIC);
+		if (!nskb)
+			return -ENOMEM;
+
+		if (!pskb_network_may_pull(nskb, sizeof(struct iphdr))) {
+			kfree_skb(nskb);
+			return -EBADMSG;
+		}
+
+		if (!skb_dst(nskb) && ip_route_reply_fill_dst(nskb) < 0) {
+			kfree_skb(nskb);
+			return -EHOSTUNREACH;
+		}
+
+		memset(IPCB(nskb), 0, sizeof(struct inet_skb_parm));
+
+		icmp_send(nskb, type, code, 0);
+		consume_skb(nskb);
+		break;
+#endif
+#if IS_ENABLED(CONFIG_IPV6)
+	case htons(ETH_P_IPV6):
+		if (type != ICMPV6_DEST_UNREACH)
+			return -EOPNOTSUPP;
+		if (code < 0 || code > ICMPV6_REJECT_ROUTE)
+			return -EINVAL;
+
+		nskb = skb_clone(skb, GFP_ATOMIC);
+		if (!nskb)
+			return -ENOMEM;
+
+		if (!pskb_network_may_pull(nskb, sizeof(struct ipv6hdr))) {
+			kfree_skb(nskb);
+			return -EBADMSG;
+		}
+
+		if (!skb_dst(nskb) && ip6_route_reply_fill_dst(nskb) < 0) {
+			kfree_skb(nskb);
+			return -EHOSTUNREACH;
+		}
+
+		memset(IP6CB(nskb), 0, sizeof(struct inet6_skb_parm));
+
+		icmpv6_send(nskb, type, code, 0);
+		consume_skb(nskb);
+		break;
+#endif
+	default:
+		return -EPROTONOSUPPORT;
+	}
+
+	return 0;
+}
+
 __bpf_kfunc_end_defs();

 int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags,
@@ -12588,6 +12685,10 @@ BTF_KFUNCS_START(bpf_kfunc_check_set_sock_ops)
 BTF_ID_FLAGS(func, bpf_sock_ops_enable_tx_tstamp)
 BTF_KFUNCS_END(bpf_kfunc_check_set_sock_ops)

+BTF_KFUNCS_START(bpf_kfunc_check_set_icmp_send)
+BTF_ID_FLAGS(func, bpf_icmp_send)
+BTF_KFUNCS_END(bpf_kfunc_check_set_icmp_send)
+
 static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
 	.owner = THIS_MODULE,
 	.set = &bpf_kfunc_check_set_skb,
@@ -12618,6 +12719,11 @@ static const struct btf_kfunc_id_set bpf_kfunc_set_sock_ops = {
 	.set = &bpf_kfunc_check_set_sock_ops,
 };

+static const struct btf_kfunc_id_set bpf_kfunc_set_icmp_send = {
+	.owner = THIS_MODULE,
+	.set = &bpf_kfunc_check_set_icmp_send,
+};
+
 static int __init bpf_kfunc_init(void)
 {
 	int ret;
@@ -12639,6 +12745,9 @@ static int __init bpf_kfunc_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
 					       &bpf_kfunc_set_sock_addr);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_tcp_reqsk);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SKB, &bpf_kfunc_set_icmp_send);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_icmp_send);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_ACT, &bpf_kfunc_set_icmp_send);
 	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SOCK_OPS, &bpf_kfunc_set_sock_ops);
 }
 late_initcall(bpf_kfunc_init);
--
2.34.1

[PATCH bpf-next v8 4/7] selftests/bpf: add bpf_icmp_send kfunc cgroup_skb tests

[Mahe Tardy]

This test opens a server and client, enters a new cgroup, attach a
cgroup_skb program on egress and calls the bpf_icmp_send function from
the client egress so that an ICMP unreach control message is sent back
to the client. It then fetches the message from the error queue to
confirm the correct ICMP unreach code has been sent.

Note that, for the client, we have to connect in non-blocking mode to
let the test execute faster. Otherwise, we need to wait for the TCP
three-way handshake to timeout in the kernel before reading the errno.

Also note that we don't set IP_RECVERR on the socket in
connect_to_fd_nonblock since the error will be transferred anyway in our
test because the connection is rejected at the beginning of the TCP
handshake. See in net/ipv4/tcp_ipv4.c:tcp_v4_err for more details.

Reviewed-by: Jordan Rife <jordan@jrife.io>
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 .../bpf/prog_tests/icmp_send_kfunc.c          | 151 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/icmp_send.c |  38 +++++
 2 files changed, 189 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/progs/icmp_send.c

diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
new file mode 100644
index 000000000000..f4e5b883d4c8
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+#include <linux/errqueue.h>
+#include <poll.h>
+#include "icmp_send.skel.h"
+
+#define TIMEOUT_MS 1000
+
+#define ICMP_DEST_UNREACH 3
+
+#define ICMP_FRAG_NEEDED 4
+#define NR_ICMP_UNREACH 15
+
+static int connect_to_fd_nonblock(int server_fd)
+{
+	struct sockaddr_storage addr;
+	socklen_t len = sizeof(addr);
+	int fd, err;
+
+	if (getsockname(server_fd, (struct sockaddr *)&addr, &len))
+		return -1;
+
+	fd = socket(addr.ss_family, SOCK_STREAM | SOCK_NONBLOCK, 0);
+	if (fd < 0)
+		return -1;
+
+	err = connect(fd, (struct sockaddr *)&addr, len);
+	if (err < 0 && errno != EINPROGRESS) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
+static void read_icmp_errqueue(int sockfd, int expected_code)
+{
+	struct sock_extended_err *sock_err;
+	char ctrl_buf[512];
+	struct msghdr msg = {
+		.msg_control = ctrl_buf,
+		.msg_controllen = sizeof(ctrl_buf),
+	};
+	struct pollfd pfd = {
+		.fd = sockfd,
+		.events = POLLERR,
+	};
+	struct cmsghdr *cm;
+	ssize_t n;
+
+	if (!ASSERT_GE(poll(&pfd, 1, TIMEOUT_MS), 1, "poll_errqueue"))
+		return;
+
+	n = recvmsg(sockfd, &msg, MSG_ERRQUEUE);
+	if (!ASSERT_GE(n, 0, "recvmsg_errqueue"))
+		return;
+
+	cm = CMSG_FIRSTHDR(&msg);
+	if (!ASSERT_NEQ(cm, NULL, "cm_firsthdr_null"))
+		return;
+
+	for (; cm; cm = CMSG_NXTHDR(&msg, cm)) {
+		if (cm->cmsg_level != IPPROTO_IP || cm->cmsg_type != IP_RECVERR)
+			continue;
+
+		sock_err = (struct sock_extended_err *)CMSG_DATA(cm);
+
+		if (!ASSERT_EQ(sock_err->ee_origin, SO_EE_ORIGIN_ICMP,
+			       "sock_err_origin_icmp"))
+			return;
+		if (!ASSERT_EQ(sock_err->ee_type, ICMP_DEST_UNREACH,
+			       "sock_err_type_dest_unreach"))
+			return;
+		ASSERT_EQ(sock_err->ee_code, expected_code, "sock_err_code");
+		return;
+	}
+
+	ASSERT_FAIL("no IP_RECVERR/IPV6_RECVERR control message found");
+}
+
+static void trigger_prog_read_icmp_errqueue(struct icmp_send *skel, int code)
+{
+	int srv_fd = -1, client_fd = -1;
+	struct sockaddr_in addr;
+	socklen_t len = sizeof(addr);
+
+	srv_fd = start_server(AF_INET, SOCK_STREAM, "127.0.0.1", 0, TIMEOUT_MS);
+	if (!ASSERT_OK_FD(srv_fd, "start_server"))
+		return;
+
+	if (getsockname(srv_fd, (struct sockaddr *)&addr, &len)) {
+		close(srv_fd);
+		return;
+	}
+	skel->bss->server_port = ntohs(addr.sin_port);
+	skel->bss->unreach_code = code;
+
+	client_fd = connect_to_fd_nonblock(srv_fd);
+	if (!ASSERT_OK_FD(client_fd, "client_connect_nonblock")) {
+		close(srv_fd);
+		return;
+	}
+
+	/* Skip reading ICMP error queue if code is invalid */
+	if (code >= 0 && code <= NR_ICMP_UNREACH)
+		read_icmp_errqueue(client_fd, code);
+
+	close(client_fd);
+	close(srv_fd);
+}
+
+void test_icmp_send_unreach_cgroup(void)
+{
+	struct icmp_send *skel;
+	int cgroup_fd = -1;
+
+	skel = icmp_send__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		goto cleanup;
+
+	cgroup_fd = test__join_cgroup("/icmp_send_unreach_cgroup");
+	if (!ASSERT_OK_FD(cgroup_fd, "join_cgroup"))
+		goto cleanup;
+
+	skel->links.egress =
+		bpf_program__attach_cgroup(skel->progs.egress, cgroup_fd);
+	if (!ASSERT_OK_PTR(skel->links.egress, "prog_attach_cgroup"))
+		goto cleanup;
+
+	for (int code = 0; code <= NR_ICMP_UNREACH; code++) {
+		/*
+		 * The TCP stack reacts differently when asking for
+		 * fragmentation, let's ignore it for now.
+		 */
+		if (code == ICMP_FRAG_NEEDED)
+			continue;
+
+		trigger_prog_read_icmp_errqueue(skel, code);
+		ASSERT_EQ(skel->data->kfunc_ret, 0, "kfunc_ret");
+	}
+
+	/* Test an invalid code */
+	trigger_prog_read_icmp_errqueue(skel, -1);
+	ASSERT_EQ(skel->data->kfunc_ret, -EINVAL, "kfunc_ret");
+
+cleanup:
+	icmp_send__destroy(skel);
+	if (cgroup_fd >= 0)
+		close(cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/icmp_send.c b/tools/testing/selftests/bpf/progs/icmp_send.c
new file mode 100644
index 000000000000..6d0be0a9afe1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/icmp_send.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+/* 127.0.0.1 in host byte order */
+#define SERVER_IP 0x7F000001
+
+#define ICMP_DEST_UNREACH 3
+
+__u16 server_port = 0;
+int unreach_code = 0;
+int kfunc_ret = -1;
+
+SEC("cgroup_skb/egress")
+int egress(struct __sk_buff *skb)
+{
+	void *data = (void *)(long)skb->data;
+	void *data_end = (void *)(long)skb->data_end;
+	struct iphdr *iph;
+	struct tcphdr *tcph;
+
+	iph = data;
+	if ((void *)(iph + 1) > data_end || iph->version != 4 ||
+	    iph->protocol != IPPROTO_TCP || iph->daddr != bpf_htonl(SERVER_IP))
+		return SK_PASS;
+
+	tcph = (void *)iph + iph->ihl * 4;
+	if ((void *)(tcph + 1) > data_end ||
+	    tcph->dest != bpf_htons(server_port))
+		return SK_PASS;
+
+	kfunc_ret = bpf_icmp_send(skb, ICMP_DEST_UNREACH, unreach_code);
+
+	return SK_DROP;
+}
+
+char LICENSE[] SEC("license") = "Dual BSD/GPL";
--
2.34.1

[PATCH bpf-next v8 5/7] selftests/bpf: add bpf_icmp_send kfunc cgroup_skb IPv6 tests

[Mahe Tardy]

This test extends the existing cgroup_skb tests with IPv6 support.

Note that we need to set IPV6_RECVERR on the socket for IPv6 in
connect_to_fd_nonblock otherwise the error will be ignored even if we
are in the middle of the TCP handshake. See in
net/ipv6/datagram.c:ipv6_icmp_error for more details.

Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 .../bpf/prog_tests/icmp_send_kfunc.c          | 77 +++++++++++++------
 tools/testing/selftests/bpf/progs/icmp_send.c | 48 +++++++++---
 2 files changed, 92 insertions(+), 33 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
index f4e5b883d4c8..a5ac1a6ea77a 100644
--- a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
@@ -8,15 +8,17 @@
 #define TIMEOUT_MS 1000

 #define ICMP_DEST_UNREACH 3
+#define ICMPV6_DEST_UNREACH 1

 #define ICMP_FRAG_NEEDED 4
 #define NR_ICMP_UNREACH 15
+#define ICMPV6_REJECT_ROUTE 6

 static int connect_to_fd_nonblock(int server_fd)
 {
 	struct sockaddr_storage addr;
 	socklen_t len = sizeof(addr);
-	int fd, err;
+	int fd, err, on = 1;

 	if (getsockname(server_fd, (struct sockaddr *)&addr, &len))
 		return -1;
@@ -25,6 +27,12 @@ static int connect_to_fd_nonblock(int server_fd)
 	if (fd < 0)
 		return -1;

+	if (addr.ss_family == AF_INET6 &&
+	    setsockopt(fd, IPPROTO_IPV6, IPV6_RECVERR, &on, sizeof(on)) < 0) {
+		close(fd);
+		return -1;
+	}
+
 	err = connect(fd, (struct sockaddr *)&addr, len);
 	if (err < 0 && errno != EINPROGRESS) {
 		close(fd);
@@ -34,8 +42,14 @@ static int connect_to_fd_nonblock(int server_fd)
 	return fd;
 }

-static void read_icmp_errqueue(int sockfd, int expected_code)
+static void read_icmp_errqueue(int sockfd, int expected_code, int af)
 {
+	int expected_ee_type = (af == AF_INET) ? ICMP_DEST_UNREACH :
+						 ICMPV6_DEST_UNREACH;
+	int expected_origin = (af == AF_INET) ? SO_EE_ORIGIN_ICMP :
+						SO_EE_ORIGIN_ICMP6;
+	int expected_level = (af == AF_INET) ? IPPROTO_IP : IPPROTO_IPV6;
+	int expected_type = (af == AF_INET) ? IP_RECVERR : IPV6_RECVERR;
 	struct sock_extended_err *sock_err;
 	char ctrl_buf[512];
 	struct msghdr msg = {
@@ -61,15 +75,16 @@ static void read_icmp_errqueue(int sockfd, int expected_code)
 		return;

 	for (; cm; cm = CMSG_NXTHDR(&msg, cm)) {
-		if (cm->cmsg_level != IPPROTO_IP || cm->cmsg_type != IP_RECVERR)
+		if (cm->cmsg_level != expected_level ||
+		    cm->cmsg_type != expected_type)
 			continue;

 		sock_err = (struct sock_extended_err *)CMSG_DATA(cm);

-		if (!ASSERT_EQ(sock_err->ee_origin, SO_EE_ORIGIN_ICMP,
-			       "sock_err_origin_icmp"))
+		if (!ASSERT_EQ(sock_err->ee_origin, expected_origin,
+			       "sock_err_origin"))
 			return;
-		if (!ASSERT_EQ(sock_err->ee_type, ICMP_DEST_UNREACH,
+		if (!ASSERT_EQ(sock_err->ee_type, expected_ee_type,
 			       "sock_err_type_dest_unreach"))
 			return;
 		ASSERT_EQ(sock_err->ee_code, expected_code, "sock_err_code");
@@ -79,13 +94,14 @@ static void read_icmp_errqueue(int sockfd, int expected_code)
 	ASSERT_FAIL("no IP_RECVERR/IPV6_RECVERR control message found");
 }

-static void trigger_prog_read_icmp_errqueue(struct icmp_send *skel, int code)
+static void trigger_prog_read_icmp_errqueue(struct icmp_send *skel, int code,
+					    int af, const char *ip)
 {
 	int srv_fd = -1, client_fd = -1;
 	struct sockaddr_in addr;
 	socklen_t len = sizeof(addr);

-	srv_fd = start_server(AF_INET, SOCK_STREAM, "127.0.0.1", 0, TIMEOUT_MS);
+	srv_fd = start_server(af, SOCK_STREAM, ip, 0, TIMEOUT_MS);
 	if (!ASSERT_OK_FD(srv_fd, "start_server"))
 		return;

@@ -94,6 +110,8 @@ static void trigger_prog_read_icmp_errqueue(struct icmp_send *skel, int code)
 		return;
 	}
 	skel->bss->server_port = ntohs(addr.sin_port);
+	skel->bss->unreach_type = (af == AF_INET) ? ICMP_DEST_UNREACH :
+						    ICMPV6_DEST_UNREACH;
 	skel->bss->unreach_code = code;

 	client_fd = connect_to_fd_nonblock(srv_fd);
@@ -103,13 +121,34 @@ static void trigger_prog_read_icmp_errqueue(struct icmp_send *skel, int code)
 	}

 	/* Skip reading ICMP error queue if code is invalid */
-	if (code >= 0 && code <= NR_ICMP_UNREACH)
-		read_icmp_errqueue(client_fd, code);
+	if (code >= 0 && ((af == AF_INET && code <= NR_ICMP_UNREACH) ||
+			  (af == AF_INET6 && code <= ICMPV6_REJECT_ROUTE)))
+		read_icmp_errqueue(client_fd, code, af);

 	close(client_fd);
 	close(srv_fd);
 }

+static void run_icmp_test(struct icmp_send *skel, int af, const char *ip,
+			  int max_code)
+{
+	for (int code = 0; code <= max_code; code++) {
+		/*
+		 * The TCP stack reacts differently when asking for
+		 * fragmentation, let's ignore it for now.
+		 */
+		if (af == AF_INET && code == ICMP_FRAG_NEEDED)
+			continue;
+
+		trigger_prog_read_icmp_errqueue(skel, code, af, ip);
+		ASSERT_EQ(skel->data->kfunc_ret, 0, "kfunc_ret");
+	}
+
+	/* Test an invalid code */
+	trigger_prog_read_icmp_errqueue(skel, -1, af, ip);
+	ASSERT_EQ(skel->data->kfunc_ret, -EINVAL, "kfunc_ret");
+}
+
 void test_icmp_send_unreach_cgroup(void)
 {
 	struct icmp_send *skel;
@@ -128,21 +167,11 @@ void test_icmp_send_unreach_cgroup(void)
 	if (!ASSERT_OK_PTR(skel->links.egress, "prog_attach_cgroup"))
 		goto cleanup;

-	for (int code = 0; code <= NR_ICMP_UNREACH; code++) {
-		/*
-		 * The TCP stack reacts differently when asking for
-		 * fragmentation, let's ignore it for now.
-		 */
-		if (code == ICMP_FRAG_NEEDED)
-			continue;
-
-		trigger_prog_read_icmp_errqueue(skel, code);
-		ASSERT_EQ(skel->data->kfunc_ret, 0, "kfunc_ret");
-	}
+	if (test__start_subtest("ipv4"))
+		run_icmp_test(skel, AF_INET, "127.0.0.1", NR_ICMP_UNREACH);

-	/* Test an invalid code */
-	trigger_prog_read_icmp_errqueue(skel, -1);
-	ASSERT_EQ(skel->data->kfunc_ret, -EINVAL, "kfunc_ret");
+	if (test__start_subtest("ipv6"))
+		run_icmp_test(skel, AF_INET6, "::1", ICMPV6_REJECT_ROUTE);

 cleanup:
 	icmp_send__destroy(skel);
diff --git a/tools/testing/selftests/bpf/progs/icmp_send.c b/tools/testing/selftests/bpf/progs/icmp_send.c
index 6d0be0a9afe1..6e1ba539eeb0 100644
--- a/tools/testing/selftests/bpf/progs/icmp_send.c
+++ b/tools/testing/selftests/bpf/progs/icmp_send.c
@@ -5,10 +5,11 @@

 /* 127.0.0.1 in host byte order */
 #define SERVER_IP 0x7F000001
-
-#define ICMP_DEST_UNREACH 3
+/* ::1 in host byte order (last 32-bit word) */
+#define SERVER_IP6_LO 0x00000001

 __u16 server_port = 0;
+int unreach_type = 0;
 int unreach_code = 0;
 int kfunc_ret = -1;

@@ -18,19 +19,48 @@ int egress(struct __sk_buff *skb)
 	void *data = (void *)(long)skb->data;
 	void *data_end = (void *)(long)skb->data_end;
 	struct iphdr *iph;
+	struct ipv6hdr *ip6h;
 	struct tcphdr *tcph;
+	__u8 version;

-	iph = data;
-	if ((void *)(iph + 1) > data_end || iph->version != 4 ||
-	    iph->protocol != IPPROTO_TCP || iph->daddr != bpf_htonl(SERVER_IP))
+	if (data + 1 > data_end)
 		return SK_PASS;

-	tcph = (void *)iph + iph->ihl * 4;
-	if ((void *)(tcph + 1) > data_end ||
-	    tcph->dest != bpf_htons(server_port))
+	version = (*((__u8 *)data)) >> 4;
+
+	if (version == 4) {
+		iph = data;
+		if ((void *)(iph + 1) > data_end ||
+		    iph->protocol != IPPROTO_TCP ||
+		    iph->daddr != bpf_htonl(SERVER_IP))
+			return SK_PASS;
+
+		tcph = (void *)iph + iph->ihl * 4;
+		if ((void *)(tcph + 1) > data_end ||
+		    tcph->dest != bpf_htons(server_port))
+			return SK_PASS;
+
+	} else if (version == 6) {
+		ip6h = data;
+		if ((void *)(ip6h + 1) > data_end ||
+		    ip6h->nexthdr != IPPROTO_TCP)
+			return SK_PASS;
+
+		if (ip6h->daddr.in6_u.u6_addr32[0] != 0 ||
+		    ip6h->daddr.in6_u.u6_addr32[1] != 0 ||
+		    ip6h->daddr.in6_u.u6_addr32[2] != 0 ||
+		    ip6h->daddr.in6_u.u6_addr32[3] != bpf_htonl(SERVER_IP6_LO))
+			return SK_PASS;
+
+		tcph = (void *)(ip6h + 1);
+		if ((void *)(tcph + 1) > data_end ||
+		    tcph->dest != bpf_htons(server_port))
+			return SK_PASS;
+	} else {
 		return SK_PASS;
+	}

-	kfunc_ret = bpf_icmp_send(skb, ICMP_DEST_UNREACH, unreach_code);
+	kfunc_ret = bpf_icmp_send(skb, unreach_type, unreach_code);

 	return SK_DROP;
 }
--
2.34.1

[PATCH bpf-next v8 6/7] selftests/bpf: add bpf_icmp_send kfunc tc tests

[Mahe Tardy]

This test is similar to the one with cgroup_skb programs but uses tc
egress instead.

Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 .../bpf/prog_tests/icmp_send_kfunc.c          | 25 ++++++++
 tools/testing/selftests/bpf/progs/icmp_send.c | 60 +++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
index a5ac1a6ea77a..66447681f72d 100644
--- a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
@@ -178,3 +178,28 @@ void test_icmp_send_unreach_cgroup(void)
 	if (cgroup_fd >= 0)
 		close(cgroup_fd);
 }
+
+void test_icmp_send_unreach_tc(void)
+{
+	LIBBPF_OPTS(bpf_tcx_opts, opts);
+	struct icmp_send *skel;
+	struct bpf_link *link = NULL;
+
+	skel = icmp_send__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		goto cleanup;
+
+	link = bpf_program__attach_tcx(skel->progs.tc_egress, 1, &opts);
+	if (!ASSERT_OK_PTR(link, "prog_attach"))
+		goto cleanup;
+
+	if (test__start_subtest("ipv4"))
+		run_icmp_test(skel, AF_INET, "127.0.0.1", NR_ICMP_UNREACH);
+
+	if (test__start_subtest("ipv6"))
+		run_icmp_test(skel, AF_INET6, "::1", ICMPV6_REJECT_ROUTE);
+
+cleanup:
+	bpf_link__destroy(link);
+	icmp_send__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/icmp_send.c b/tools/testing/selftests/bpf/progs/icmp_send.c
index 6e1ba539eeb0..5fa5467bdb70 100644
--- a/tools/testing/selftests/bpf/progs/icmp_send.c
+++ b/tools/testing/selftests/bpf/progs/icmp_send.c
@@ -2,6 +2,7 @@
 #include "vmlinux.h"
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
+#include "bpf_tracing_net.h"

 /* 127.0.0.1 in host byte order */
 #define SERVER_IP 0x7F000001
@@ -65,4 +66,63 @@ int egress(struct __sk_buff *skb)
 	return SK_DROP;
 }

+SEC("tc/egress")
+int tc_egress(struct __sk_buff *skb)
+{
+	void *data = (void *)(long)skb->data;
+	void *data_end = (void *)(long)skb->data_end;
+	struct ethhdr *eth;
+	struct iphdr *iph;
+	struct ipv6hdr *ip6h;
+	struct tcphdr *tcph;
+
+	eth = data;
+	if ((void *)(eth + 1) > data_end)
+		return TCX_PASS;
+
+	if (eth->h_proto == bpf_htons(ETH_P_IP)) {
+		iph = (void *)(eth + 1);
+		if ((void *)(iph + 1) > data_end)
+			return TCX_PASS;
+
+		if (iph->protocol != IPPROTO_TCP ||
+		    iph->daddr != bpf_htonl(SERVER_IP))
+			return TCX_PASS;
+
+		tcph = (void *)iph + iph->ihl * 4;
+		if ((void *)(tcph + 1) > data_end)
+			return TCX_PASS;
+
+		if (tcph->dest != bpf_htons(server_port))
+			return TCX_PASS;
+
+	} else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
+		ip6h = (void *)(eth + 1);
+		if ((void *)(ip6h + 1) > data_end)
+			return TCX_PASS;
+
+		if (ip6h->nexthdr != IPPROTO_TCP)
+			return TCX_PASS;
+
+		if (ip6h->daddr.in6_u.u6_addr32[0] != 0 ||
+		    ip6h->daddr.in6_u.u6_addr32[1] != 0 ||
+		    ip6h->daddr.in6_u.u6_addr32[2] != 0 ||
+		    ip6h->daddr.in6_u.u6_addr32[3] != bpf_htonl(SERVER_IP6_LO))
+			return TCX_PASS;
+
+		tcph = (void *)(ip6h + 1);
+		if ((void *)(tcph + 1) > data_end)
+			return TCX_PASS;
+
+		if (tcph->dest != bpf_htons(server_port))
+			return TCX_PASS;
+	} else {
+		return TCX_PASS;
+	}
+
+	kfunc_ret = bpf_icmp_send(skb, unreach_type, unreach_code);
+
+	return TCX_DROP;
+}
+
 char LICENSE[] SEC("license") = "Dual BSD/GPL";
--
2.34.1

[PATCH bpf-next v8 7/7] selftests/bpf: add bpf_icmp_send recursion test

[Mahe Tardy]

This test is similar to test_icmp_send_unreach_cgroup but checks that,
in case of recursion, meaning that the BPF program calling the kfunc was
re-triggered by the icmp_send done by the kfunc, the kfunc will stop
early and return -EBUSY.

The test attaches to the root cgroup to ensure the ICMP packet generated
by the kfunc re-triggers the BPF program. Since it's attached only for
this recursion test, it should not disrupt the whole network.

Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 .../bpf/prog_tests/icmp_send_kfunc.c          | 45 +++++++++++++++
 tools/testing/selftests/bpf/progs/icmp_send.c | 56 +++++++++++++++++++
 2 files changed, 101 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
index 66447681f72d..fd4b8fa78a01 100644
--- a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
@@ -1,8 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
 #include <network_helpers.h>
+#include <cgroup_helpers.h>
 #include <linux/errqueue.h>
 #include <poll.h>
+#include <unistd.h>
 #include "icmp_send.skel.h"

 #define TIMEOUT_MS 1000
@@ -10,6 +12,7 @@
 #define ICMP_DEST_UNREACH 3
 #define ICMPV6_DEST_UNREACH 1

+#define ICMP_HOST_UNREACH 1
 #define ICMP_FRAG_NEEDED 4
 #define NR_ICMP_UNREACH 15
 #define ICMPV6_REJECT_ROUTE 6
@@ -203,3 +206,45 @@ void test_icmp_send_unreach_tc(void)
 	bpf_link__destroy(link);
 	icmp_send__destroy(skel);
 }
+
+void test_icmp_send_unreach_recursion(void)
+{
+	struct icmp_send *skel;
+	int cgroup_fd = -1;
+
+	skel = icmp_send__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		goto cleanup;
+
+	if (setup_cgroup_environment()) {
+		fprintf(stderr, "Failed to setup cgroup environment\n");
+		goto cleanup;
+	}
+
+	cgroup_fd = get_root_cgroup();
+	if (!ASSERT_OK_FD(cgroup_fd, "get_root_cgroup"))
+		goto cleanup;
+
+	skel->data->target_pid = getpid();
+	skel->links.recursion =
+		bpf_program__attach_cgroup(skel->progs.recursion, cgroup_fd);
+	if (!ASSERT_OK_PTR(skel->links.recursion, "prog_attach_cgroup"))
+		goto cleanup;
+
+	trigger_prog_read_icmp_errqueue(skel, ICMP_HOST_UNREACH, AF_INET,
+					"127.0.0.1");
+
+	/*
+	 * Because there's recursion involved, the first call will return at
+	 * index 1 since it will return the second, and the second call will
+	 * return at index 0 since it will return the first.
+	 */
+	ASSERT_EQ(skel->data->rec_kfunc_rets[0], -EBUSY, "kfunc_rets[0]");
+	ASSERT_EQ(skel->data->rec_kfunc_rets[1], 0, "kfunc_rets[1]");
+
+cleanup:
+	cleanup_cgroup_environment();
+	icmp_send__destroy(skel);
+	if (cgroup_fd >= 0)
+		close(cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/icmp_send.c b/tools/testing/selftests/bpf/progs/icmp_send.c
index 5fa5467bdb70..fd9c7684797b 100644
--- a/tools/testing/selftests/bpf/progs/icmp_send.c
+++ b/tools/testing/selftests/bpf/progs/icmp_send.c
@@ -13,6 +13,10 @@ __u16 server_port = 0;
 int unreach_type = 0;
 int unreach_code = 0;
 int kfunc_ret = -1;
+int target_pid = -1;
+
+unsigned int rec_count = 0;
+int rec_kfunc_rets[] = { -1, -1 };

 SEC("cgroup_skb/egress")
 int egress(struct __sk_buff *skb)
@@ -125,4 +129,56 @@ int tc_egress(struct __sk_buff *skb)
 	return TCX_DROP;
 }

+SEC("cgroup_skb/egress")
+int recursion(struct __sk_buff *skb)
+{
+	void *data = (void *)(long)skb->data;
+	void *data_end = (void *)(long)skb->data_end;
+	struct icmphdr *icmph;
+	struct tcphdr *tcph;
+	struct iphdr *iph;
+	int ret;
+
+	if ((bpf_get_current_pid_tgid() >> 32) != target_pid)
+		return SK_PASS;
+
+	iph = data;
+	if ((void *)(iph + 1) > data_end || iph->version != 4)
+		return SK_PASS;
+
+	if (iph->daddr != bpf_htonl(SERVER_IP))
+		return SK_PASS;
+
+	if (iph->protocol == IPPROTO_TCP) {
+		tcph = (void *)iph + iph->ihl * 4;
+		if ((void *)(tcph + 1) > data_end ||
+		    tcph->dest != bpf_htons(server_port))
+			return SK_PASS;
+	} else if (iph->protocol == IPPROTO_ICMP) {
+		icmph = (void *)iph + iph->ihl * 4;
+		if ((void *)(icmph + 1) > data_end ||
+		    icmph->type != unreach_type ||
+		    icmph->code != unreach_code)
+			return SK_PASS;
+	} else {
+		return SK_PASS;
+	}
+
+	/*
+	 * This call will provoke a recursion: the ICMP packet generated by the
+	 * kfunc will re-trigger this program since we are in the root cgroup in
+	 * which the kernel ICMP socket belongs. However when re-entering the
+	 * kfunc, it should return EBUSY.
+	 */
+	ret = bpf_icmp_send(skb, unreach_type, unreach_code);
+	rec_kfunc_rets[rec_count & 1] = ret;
+	__sync_fetch_and_add(&rec_count, 1);
+
+	/* Let the first ICMP error message pass */
+	if (iph->protocol == IPPROTO_ICMP)
+		return SK_PASS;
+
+	return SK_DROP;
+}
+
 char LICENSE[] SEC("license") = "Dual BSD/GPL";
--
2.34.1

Re: [PATCH bpf-next v8 4/7] selftests/bpf: add bpf_icmp_send kfunc cgroup_skb tests

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1280 bytes --]

> diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
> new file mode 100644
> index 000000000000..f4e5b883d4c8
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c

[ ... ]

> +static void read_icmp_errqueue(int sockfd, int expected_code)
> +{

[ ... ]

> +	for (; cm; cm = CMSG_NXTHDR(&msg, cm)) {
> +		if (cm->cmsg_level != IPPROTO_IP || cm->cmsg_type != IP_RECVERR)
> +			continue;

[ ... ]

> +	}
> +
> +	ASSERT_FAIL("no IP_RECVERR/IPV6_RECVERR control message found");

This isn't a bug, but the failure string names both IP_RECVERR and
IPV6_RECVERR:

	ASSERT_FAIL("no IP_RECVERR/IPV6_RECVERR control message found");

while the loop above only matches IPv4:

	if (cm->cmsg_level != IPPROTO_IP || cm->cmsg_type != IP_RECVERR)
		continue;

and the caller is AF_INET only (start_server(AF_INET, ...) with a
struct sockaddr_in).

Should the IPV6_RECVERR part of the string be dropped to match what the
code actually inspects?

> +}

---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/27951892371

Re: [PATCH bpf-next v8 6/7] selftests/bpf: add bpf_icmp_send kfunc tc tests

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1622 bytes --]

> diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
> index a5ac1a6ea77a..66447681f72d 100644
> --- a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
> +++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
> @@ -178,3 +178,28 @@ void test_icmp_send_unreach_cgroup(void)
>  	if (cgroup_fd >= 0)
>  		close(cgroup_fd);
>  }
> +
> +void test_icmp_send_unreach_tc(void)
> +{
> +	LIBBPF_OPTS(bpf_tcx_opts, opts);
> +	struct icmp_send *skel;
> +	struct bpf_link *link = NULL;
> +
> +	skel = icmp_send__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel_open"))
> +		goto cleanup;
> +
> +	link = bpf_program__attach_tcx(skel->progs.tc_egress, 1, &opts);

This isn't a bug, but would a named constant read more clearly here than
the bare ifindex literal 1? Looking at prog_tests/tc_change_tail.c, it
defines LO_IFINDEX for this same purpose, and prog_tests/tc_links.c
resolves the loopback interface via if_nametoindex("lo").

> +	if (!ASSERT_OK_PTR(link, "prog_attach"))
> +		goto cleanup;
> +
> +	if (test__start_subtest("ipv4"))
> +		run_icmp_test(skel, AF_INET, "127.0.0.1", NR_ICMP_UNREACH);
> +
> +	if (test__start_subtest("ipv6"))
> +		run_icmp_test(skel, AF_INET6, "::1", ICMPV6_REJECT_ROUTE);
> +
> +cleanup:
> +	bpf_link__destroy(link);
> +	icmp_send__destroy(skel);
> +}

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/27951892371