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tcp: fix TCP socket rehash stats mis-accounting 

The previous commit 32efcc06d2 ("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: 32efcc06d2 ("tcp: export count for rehash attempts")
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Link: https://lore.kernel.org/r/20210119192619.1848270-1-ycheng@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Yuchung Cheng 2021-01-19 11:26:19 -08:00 committed by Jakub Kicinski
parent 8e4052c32d
commit 9c30ae8398
3 changed files with 22 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/net/sock.h
View File

@ -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)
{

5
net/ipv4/tcp_input.c
View File

@ -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)

22
net/ipv4/tcp_timer.c
View File

@ -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;
}