From d44fd4a767b3755899f8ad1df3e8eca3961ba708 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 4 Aug 2023 14:46:11 +0000 Subject: [PATCH] tcp: set TCP_SYNCNT locklessly icsk->icsk_syn_retries can safely be set without locking the socket. We have to add READ_ONCE() annotations in tcp_fastopen_synack_timer() and tcp_write_timeout(). Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 15 ++++++--------- net/ipv4/tcp_timer.c | 9 ++++++--- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index aca5620..bcbb33a 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3291,9 +3291,7 @@ int tcp_sock_set_syncnt(struct sock *sk, int val) if (val < 1 || val > MAX_TCP_SYNCNT) return -EINVAL; - lock_sock(sk); WRITE_ONCE(inet_csk(sk)->icsk_syn_retries, val); - release_sock(sk); return 0; } EXPORT_SYMBOL(tcp_sock_set_syncnt); @@ -3462,6 +3460,12 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname, if (copy_from_sockptr(&val, optval, sizeof(val))) return -EFAULT; + /* Handle options that can be set without locking the socket. */ + switch (optname) { + case TCP_SYNCNT: + return tcp_sock_set_syncnt(sk, val); + } + sockopt_lock_sock(sk); switch (optname) { @@ -3569,13 +3573,6 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname, else WRITE_ONCE(tp->keepalive_probes, val); break; - case TCP_SYNCNT: - if (val < 1 || val > MAX_TCP_SYNCNT) - err = -EINVAL; - else - WRITE_ONCE(icsk->icsk_syn_retries, val); - break; - case TCP_SAVE_SYN: /* 0: disable, 1: enable, 2: start from ether_header */ if (val < 0 || val > 2) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 470f581..66040ab 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -239,7 +239,8 @@ static int tcp_write_timeout(struct sock *sk) if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { if (icsk->icsk_retransmits) __dst_negative_advice(sk); - retry_until = icsk->icsk_syn_retries ? : + /* Paired with WRITE_ONCE() in tcp_sock_set_syncnt() */ + retry_until = READ_ONCE(icsk->icsk_syn_retries) ? : READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); max_retransmits = retry_until; @@ -421,8 +422,10 @@ static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) req->rsk_ops->syn_ack_timeout(req); - /* add one more retry for fastopen */ - max_retries = icsk->icsk_syn_retries ? : + /* Add one more retry for fastopen. + * Paired with WRITE_ONCE() in tcp_sock_set_syncnt() + */ + max_retries = READ_ONCE(icsk->icsk_syn_retries) ? : READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1; if (req->num_timeout >= max_retries) { -- 2.7.4