net/tcp: Add tcp_hash_fail() ratelimited logs

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>
Acked-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -2748,12 +2748,18 @@ 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) {
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOBAD);
+			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;
 		}
 	}
@@ -2770,10 +2776,14 @@ tcp_inbound_hash(struct sock *sk, const struct request_sock *req,
 		 * the last key is impossible to remove, so there's
 		 * always at least one current_key.
 		 */
-		if (tcp_ao_required(sk, saddr, family, true))
+		if (tcp_ao_required(sk, saddr, family, true)) {
+			tcp_hash_fail("AO hash is required, but not found",
+					family, skb, "L3 index %d", l3index);
 			return SKB_DROP_REASON_TCP_AONOTFOUND;
+		}
 		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;

include/net/tcp_ao.h

@@ -118,6 +118,35 @@ struct tcp_ao_info {
 	struct rcu_head		rcu;
 };
 
+#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 (f != hdr_flags)						\
+		*f = ' ';						\
+	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 */
 

net/ipv4/tcp.c

@@ -4383,7 +4383,6 @@ 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);
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
 	u8 newhash[16];
@@ -4393,6 +4392,7 @@ 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;
 	}
 
@@ -4408,16 +4408,19 @@ 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;
 	}

net/ipv4/tcp_ao.c

@@ -800,6 +800,8 @@ 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;
 	}
 
@@ -814,6 +816,7 @@ 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, "");
 		kfree(hash_buf);
 		return SKB_DROP_REASON_TCP_AOFAILURE;
 	}
@@ -841,6 +844,8 @@ 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;
 	}
 
@@ -942,6 +947,8 @@ 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;
 }