git: 1043b36b2054 - main - tcp: don't send beyond receivers advertised window

The branch main has been updated by glebius:

URL: https://cgit.FreeBSD.org/src/commit/?id=1043b36b2054ffb32aadfe1c276684bf463db59a

commit 1043b36b2054ffb32aadfe1c276684bf463db59a
Author:     Gleb Smirnoff <glebius@FreeBSD.org>
AuthorDate: 2025-01-13 18:13:54 +0000
Commit:     Gleb Smirnoff <glebius@FreeBSD.org>
CommitDate: 2025-01-13 18:13:54 +0000

    tcp: don't send beyond receivers advertised window
    
    When calculating length of data to be sent, we may do some congestion
    calculations, but we shall never send a byte beyond (snd_una + snd_wnd).
    In 7dc78150c730e we started to use tcp_compute_pipe() instead of (snd_wnd
    - off).  This function makes an estimate of how much data is in flight. It
    can return a value smaller and larger than (snd_nxt - snd_una).  It will
    return a value larger when we have retransmitted some data from SACK
    holes, and smaller once those retransmitted SACK holes are acked.
    
    We may use tcp_compute_pipe() for length calculation, but always capped
    by the send offset 'off', which (snd_nxt - snd_una).
    
    PR:                     283649
    Reviewed by:            rscheff
    Differential Revision:  https://reviews.freebsd.org/D48237
    Fixes:                  7dc78150c730e90fa2afdaba3aa645932b30c429
---
 sys/netinet/tcp_output.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 74a229012508..135e7d8493e2 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -421,8 +421,9 @@ after_sack_rexmit:
 			 * sending new data, having retransmitted all the
 			 * data possible in the scoreboard.
 			 */
-			len = imin(sbavail(&so->so_snd) - off,
-				sendwin - tcp_compute_pipe(tp));
+			len = imax(
+			    imin(sbavail(&so->so_snd), sendwin) -
+			    imax(tcp_compute_pipe(tp), off), 0);
 		}
 	}