[PATCH 20/31] net/tcp: Add tcp_hash_fail() ratelimited logs

Dmitry Safonov
2022-08-18T17:04:27Z

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 8df03d456ebb..3ef9d69fa561 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4511,7 +4511,6 @@ 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;
@@ -4521,6 +4520,7 @@ 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;
}

@@ -4536,16 +4536,19 @@ 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 3a33733a714d..4283e0193e2a 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -662,6 +662,8 @@ 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;
}

@@ -672,6 +674,7 @@ 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);
@@ -698,6 +701,8 @@ 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;
}

@@ -780,6 +785,8 @@ 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