6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paolo Abeni <pabeni@xxxxxxxxxx>
[ 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@xxxxxxxxxxxxxxxxxxxxx>
Reported-by: Stefano Brivio <sbrivio@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/705dad54e6e6e9a010e571bf58e0b35a8ae70503.1701706073.git.pabeni@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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;
}
--
2.42.0
