[PATCH v2 20/35] net/tcp: Add tcp_hash_fail() ratelimited logs

[Dmitry Safonov <dima@arista.com>]

Add a helper for logging connection-detailed messages for failed TCP
hash verification (both MD5 and AO).

Co-developed-by: Francesco Ruggeri <fruggeri@arista.com>
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Co-developed-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 include/net/tcp.h    | 14 ++++++++++++--
 include/net/tcp_ao.h | 27 +++++++++++++++++++++++++++
 net/ipv4/tcp.c       | 23 +++++++++++++----------
 net/ipv4/tcp_ao.c    |  7 +++++++
 4 files changed, 59 insertions(+), 12 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 94573219f58d..896db7ba0670 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2517,12 +2517,19 @@ tcp_inbound_hash(struct sock *sk, const struct request_sock *req,
 	int l3index;
 
 	/* Invalid option or two times meet any of auth options */
-	if (tcp_parse_auth_options(th, &md5_location, &aoh))
+	if (tcp_parse_auth_options(th, &md5_location, &aoh)) {
+		tcp_hash_fail("TCP segment has incorrect auth options set",
+				family, skb, "");
 		return SKB_DROP_REASON_TCP_AUTH_HDR;
+	}
 
 	if (req) {
-		if (tcp_rsk_used_ao(req) != !!aoh)
+		if (tcp_rsk_used_ao(req) != !!aoh) {
+			tcp_hash_fail("TCP connection can't start/end using TCP-AO",
+					family, skb, " %s",
+					!aoh ? "missing AO" : "AO signed");
 			return SKB_DROP_REASON_TCP_AOFAILURE;
+		}
 	}
 
 	/* sdif set, means packet ingressed via a device
@@ -2545,11 +2552,14 @@ tcp_inbound_hash(struct sock *sk, const struct request_sock *req,
 					lockdep_sock_is_held(sk));
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOREQUIRED);
 			atomic64_inc(&ao_info->counters.ao_required);
+			tcp_hash_fail("AO hash is required, but not found",
+					family, skb, "");
 			return SKB_DROP_REASON_TCP_AONOTFOUND;
 		}
 #endif
 		if (unlikely(tcp_md5_do_lookup(sk, l3index, saddr, family))) {
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
+			tcp_hash_fail("MD5 Hash not found", family, skb, "");
 			return SKB_DROP_REASON_TCP_MD5NOTFOUND;
 		}
 		return SKB_NOT_DROPPED_YET;
diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index dbeaa7d4e212..e99c8f300a5a 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -101,6 +101,33 @@ struct tcp_ao_info {
 int tcp_do_parse_auth_options(const struct tcphdr *th,
 			      const u8 **md5_hash, const u8 **ao_hash);
 
+#define tcp_hash_fail(msg, family, skb, fmt, ...)			\
+do {									\
+	const struct tcphdr *th = tcp_hdr(skb);				\
+	char hdr_flags[5] = {};						\
+	char *f = hdr_flags;						\
+									\
+	if (th->fin)							\
+		*f++ = 'F';						\
+	if (th->syn)							\
+		*f++ = 'S';						\
+	if (th->rst)							\
+		*f++ = 'R';						\
+	if (th->ack)							\
+		*f = 'A';						\
+	if (family == AF_INET) {					\
+		net_info_ratelimited("%s for (%pI4, %d)->(%pI4, %d) %s" fmt "\n", \
+				msg, &ip_hdr(skb)->saddr, ntohs(th->source), \
+				&ip_hdr(skb)->daddr, ntohs(th->dest),	\
+				hdr_flags, ##__VA_ARGS__);		\
+	} else {							\
+		net_info_ratelimited("%s for [%pI6c]:%u->[%pI6c]:%u %s" fmt "\n", \
+				msg, &ipv6_hdr(skb)->saddr, ntohs(th->source), \
+				&ipv6_hdr(skb)->daddr, ntohs(th->dest),	\
+				hdr_flags, ##__VA_ARGS__);		\
+	}								\
+} while (0)
+
 #ifdef CONFIG_TCP_AO
 /* TCP-AO structures and functions */
 
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7c8341419a7a..f7ad4443c350 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4517,7 +4517,6 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 	 * o MD5 hash and we're not expecting one.
 	 * o MD5 hash and its wrong.
 	 */
-	const struct tcphdr *th = tcp_hdr(skb);
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
 	int genhash;
@@ -4527,6 +4526,7 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 
 	if (!key && hash_location) {
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5UNEXPECTED);
+		tcp_hash_fail("Unexpected MD5 Hash found", family, skb, "");
 		return SKB_DROP_REASON_TCP_MD5UNEXPECTED;
 	}
 
@@ -4542,16 +4542,19 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 	if (genhash || memcmp(hash_location, newhash, 16) != 0) {
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5FAILURE);
 		if (family == AF_INET) {
-			net_info_ratelimited("MD5 Hash failed for (%pI4, %d)->(%pI4, %d)%s L3 index %d\n",
-					saddr, ntohs(th->source),
-					daddr, ntohs(th->dest),
-					genhash ? " tcp_v4_calc_md5_hash failed"
-					: "", l3index);
+			tcp_hash_fail("MD5 Hash failed", AF_INET, skb, "%s L3 index %d",
+				      genhash ? " tcp_v4_calc_md5_hash failed"
+				      : "", l3index);
 		} else {
-			net_info_ratelimited("MD5 Hash %s for [%pI6c]:%u->[%pI6c]:%u L3 index %d\n",
-					genhash ? "failed" : "mismatch",
-					saddr, ntohs(th->source),
-					daddr, ntohs(th->dest), l3index);
+			if (genhash) {
+				tcp_hash_fail("MD5 Hash failed",
+					      AF_INET6, skb, " L3 index %d",
+					      l3index);
+			} else {
+				tcp_hash_fail("MD5 Hash mismatch",
+					      AF_INET6, skb, " L3 index %d",
+					      l3index);
+			}
 		}
 		return SKB_DROP_REASON_TCP_MD5FAILURE;
 	}
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index ba94c9ad7037..700e9a8bc983 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -679,6 +679,8 @@ tcp_ao_verify_hash(const struct sock *sk, const struct sk_buff *skb,
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOBAD);
 		atomic64_inc(&info->counters.pkt_bad);
 		atomic64_inc(&key->pkt_bad);
+		tcp_hash_fail("AO hash wrong length", family, skb,
+			      " %u != %d", maclen, tcp_ao_maclen(key));
 		return SKB_DROP_REASON_TCP_AOFAILURE;
 	}
 
@@ -689,6 +691,7 @@ tcp_ao_verify_hash(const struct sock *sk, const struct sk_buff *skb,
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOBAD);
 		atomic64_inc(&info->counters.pkt_bad);
 		atomic64_inc(&key->pkt_bad);
+		tcp_hash_fail("AO hash mismatch", family, skb, "");
 		return SKB_DROP_REASON_TCP_AOFAILURE;
 	}
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOGOOD);
@@ -715,6 +718,8 @@ tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb,
 	info = rcu_dereference(tcp_sk(sk)->ao_info);
 	if (!info) {
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOKEYNOTFOUND);
+		tcp_hash_fail("AO key not found", family, skb,
+			      " keyid: %u", aoh->keyid);
 		return SKB_DROP_REASON_TCP_AOUNEXPECTED;
 	}
 
@@ -797,6 +802,8 @@ tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb,
 key_not_found:
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOKEYNOTFOUND);
 	atomic64_inc(&info->counters.key_not_found);
+	tcp_hash_fail("Requested by the peer AO key id not found",
+		      family, skb, "");
 	return SKB_DROP_REASON_TCP_AOKEYNOTFOUND;
 }
 
-- 
2.37.2