6.1-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Abeni pabeni@redhat.com
[ Upstream commit 58d3aade20cdddbac6c9707ac0f3f5f8c1278b74 ]
After the blamed commit below, if the user-space application performs window clamping when tp->rcv_wnd is 0, the TCP socket will never be able to announce a non 0 receive window, even after completely emptying the receive buffer and re-setting the window clamp to higher values.
Refactor tcp_set_window_clamp() to address the issue: when the user decreases the current clamp value, set rcv_ssthresh according to the same logic used at buffer initialization, but ensuring reserved mem provisioning.
To avoid code duplication factor-out the relevant bits from tcp_adjust_rcv_ssthresh() in a new helper and reuse it in the above scenario.
When increasing the clamp value, give the rcv_ssthresh a chance to grow according to previously implemented heuristic.
Fixes: 3aa7857fe1d7 ("tcp: enable mid stream window clamp") Reported-by: David Gibson david@gibson.dropbear.id.au Reported-by: Stefano Brivio sbrivio@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/705dad54e6e6e9a010e571bf58e0b35a8ae70503.170170607... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/tcp.h | 9 +++++++-- net/ipv4/tcp.c | 22 +++++++++++++++++++--- 2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h index 19646fdec23dc..c3d56b337f358 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1460,17 +1460,22 @@ static inline int tcp_full_space(const struct sock *sk) return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf)); }
-static inline void tcp_adjust_rcv_ssthresh(struct sock *sk) +static inline void __tcp_adjust_rcv_ssthresh(struct sock *sk, u32 new_ssthresh) { int unused_mem = sk_unused_reserved_mem(sk); struct tcp_sock *tp = tcp_sk(sk);
- tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); + tp->rcv_ssthresh = min(tp->rcv_ssthresh, new_ssthresh); if (unused_mem) tp->rcv_ssthresh = max_t(u32, tp->rcv_ssthresh, tcp_win_from_space(sk, unused_mem)); }
+static inline void tcp_adjust_rcv_ssthresh(struct sock *sk) +{ + __tcp_adjust_rcv_ssthresh(sk, 4U * tcp_sk(sk)->advmss); +} + void tcp_cleanup_rbuf(struct sock *sk, int copied); void __tcp_cleanup_rbuf(struct sock *sk, int copied);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 288678f17ccaf..58409ea2da0af 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3473,9 +3473,25 @@ int tcp_set_window_clamp(struct sock *sk, int val) return -EINVAL; tp->window_clamp = 0; } else { - tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ? - SOCK_MIN_RCVBUF / 2 : val; - tp->rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp); + u32 new_rcv_ssthresh, old_window_clamp = tp->window_clamp; + u32 new_window_clamp = val < SOCK_MIN_RCVBUF / 2 ? + SOCK_MIN_RCVBUF / 2 : val; + + if (new_window_clamp == old_window_clamp) + return 0; + + tp->window_clamp = new_window_clamp; + if (new_window_clamp < old_window_clamp) { + /* need to apply the reserved mem provisioning only + * when shrinking the window clamp + */ + __tcp_adjust_rcv_ssthresh(sk, tp->window_clamp); + + } else { + new_rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp); + tp->rcv_ssthresh = max(new_rcv_ssthresh, + tp->rcv_ssthresh); + } } return 0; }