[PATCH net] tcp: fix TCP socket rehash stats mis-accounting
From: Yuchung Cheng <hidden>
Date: 2021-01-19 19:39:29
The previous commit 32efcc06d2a1 ("tcp: export count for rehash attempts")
would mis-account rehashing SNMP and socket stats:
a. During handshake of an active open, only counts the first
SYN timeout
b. After handshake of passive and active open, stop updating
after (roughly) TCP_RETRIES1 recurring RTOs
c. After the socket aborts, over count timeout_rehash by 1
This patch fixes this by checking the rehash result from sk_rethink_txhash.
Fixes: 32efcc06d2a1 ("tcp: export count for rehash attempts")
Signed-off-by: Yuchung Cheng <redacted>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
---
include/net/sock.h | 17 ++++++++++++-----
net/ipv4/tcp_input.c | 5 ++---
net/ipv4/tcp_timer.c | 22 ++++++++--------------
3 files changed, 22 insertions(+), 22 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index bdc4323ce53c..129d200bccb4 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h@@ -1921,10 +1921,13 @@ static inline void sk_set_txhash(struct sock *sk) sk->sk_txhash = net_tx_rndhash(); } -static inline void sk_rethink_txhash(struct sock *sk) +static inline bool sk_rethink_txhash(struct sock *sk) { - if (sk->sk_txhash) + if (sk->sk_txhash) { sk_set_txhash(sk); + return true; + } + return false; } static inline struct dst_entry *
@@ -1947,12 +1950,10 @@ sk_dst_get(struct sock *sk) return dst; } -static inline void dst_negative_advice(struct sock *sk) +static inline void __dst_negative_advice(struct sock *sk) { struct dst_entry *ndst, *dst = __sk_dst_get(sk); - sk_rethink_txhash(sk); - if (dst && dst->ops->negative_advice) { ndst = dst->ops->negative_advice(dst);
@@ -1964,6 +1965,12 @@ static inline void dst_negative_advice(struct sock *sk) } } +static inline void dst_negative_advice(struct sock *sk) +{ + sk_rethink_txhash(sk); + __dst_negative_advice(sk); +} + static inline void __sk_dst_set(struct sock *sk, struct dst_entry *dst) {
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bafcab75f425..a7dfca0a38cd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -4397,10 +4397,9 @@ static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb) * The receiver remembers and reflects via DSACKs. Leverage the * DSACK state and change the txhash to re-route speculatively. */ - if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq) { - sk_rethink_txhash(sk); + if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq && + sk_rethink_txhash(sk)) NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDUPLICATEDATAREHASH); - } } static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 454732ecc8f3..faa92948441b 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c@@ -219,14 +219,8 @@ static int tcp_write_timeout(struct sock *sk) int retry_until; if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { - if (icsk->icsk_retransmits) { - dst_negative_advice(sk); - } else { - sk_rethink_txhash(sk); - tp->timeout_rehash++; - __NET_INC_STATS(sock_net(sk), - LINUX_MIB_TCPTIMEOUTREHASH); - } + if (icsk->icsk_retransmits) + __dst_negative_advice(sk); retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries; expired = icsk->icsk_retransmits >= retry_until; } else {
@@ -234,12 +228,7 @@ static int tcp_write_timeout(struct sock *sk) /* Black hole detection */ tcp_mtu_probing(icsk, sk); - dst_negative_advice(sk); - } else { - sk_rethink_txhash(sk); - tp->timeout_rehash++; - __NET_INC_STATS(sock_net(sk), - LINUX_MIB_TCPTIMEOUTREHASH); + __dst_negative_advice(sk); } retry_until = net->ipv4.sysctl_tcp_retries2;
@@ -270,6 +259,11 @@ static int tcp_write_timeout(struct sock *sk) return 1; } + if (sk_rethink_txhash(sk)) { + tp->timeout_rehash++; + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); + } + return 0; }
--
2.30.0.284.gd98b1dd5eaa7-goog