Re: git: 7146ad04f18e - main - tcp: refactor tcp_autosndbuf() and associated sysctls

On 22 Oct 2026, at 5:31, Gleb Smirnoff wrote:
> The branch main has been updated by glebius:
>
> URL: 
> https://cgit.FreeBSD.org/src/commit/?id=7146ad04f18e7f0767a4d44cff43c1c67ea98cec
>
> commit 7146ad04f18e7f0767a4d44cff43c1c67ea98cec
> Author:     Gleb Smirnoff <glebius@FreeBSD.org>
> AuthorDate: 2026-10-22 03:27:47 +0000
> Commit:     Gleb Smirnoff <glebius@FreeBSD.org>
> CommitDate: 2026-10-22 03:27:47 +0000
>
>     tcp: refactor tcp_autosndbuf() and associated sysctls
>
>     Rename tcp_sndbuf_autoscale() to tcp_autosndbuf().  This matches
>     complementary tcp_autorcvbuf() that was factored out as a separate
>     function a few months before tcp_sndbuf_autoscale() was.  Move the 
> large
>     comment to the header of the function.  Use unsigned types for all 
> sizing
>     sysctls and variables and use bool for the switching sysctl.  Add 
> a
>     comment above net.inet.tcp.sendbuf_auto_lowat (default to off) 
> providing a
>     reference to its origins.  Add DTrace probe tcp::send-autoresize,
>     complementary to the existing tcp::receive-autoresize.
>
>     Rack has its own function, just enable the DTrace probe there.
>
>     Reviewed by:            tuexen
>     Differential Revision:  https://reviews.freebsd.org/D60732
> ---
>  sys/netinet/in_kdtrace.c      |   4 ++
>  sys/netinet/in_kdtrace.h      |   1 +
>  sys/netinet/tcp_output.c      | 142 
> +++++++++++++++++++++---------------------
>  sys/netinet/tcp_stacks/bbr.c  |   2 +-
>  sys/netinet/tcp_stacks/rack.c |   5 +-
>  sys/netinet/tcp_var.h         |  10 +--
>  6 files changed, 85 insertions(+), 79 deletions(-)
>
…
> index 09295544855f..d11a2b745382 100644
> --- a/sys/netinet/tcp_output.c
> +++ b/sys/netinet/tcp_output.c
…
>  void
> -tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t 
> sendwin)
> +tcp_autosndbuf(struct tcpcb *tp, u_int sendwin)
>  {
>
…
> +	SOCK_RECVBUF_LOCK_ASSERT(so);
> +
Is this assert right? I’d think autosndbuf is about the send buffer, 
not the receive buffer.
I’m seeing this panic whenever I try to ssh into my dev box:

	panic: mutex so_rcv not owned at /usr/src/sys/netinet/tcp_output.c:2157
	cpuid = 4
	time = 1792657806
	KDB: stack backtrace:
	db_trace_self_wrapper() at db_trace_self_wrapper+0x36/frame 
0xfffffe00343b34a0
	vpanic() at vpanic+0x149/frame 0xfffffe00343b35d0
	panic() at panic+0x43/frame 0xfffffe00343b3630
	__mtx_assert() at __mtx_assert+0xa9/frame 0xfffffe00343b3640
	tcp_autosndbuf() at tcp_autosndbuf+0x32/frame 0xfffffe00343b3670
	tcp_default_output() at tcp_default_output+0x651/frame 
0xfffffe00343b3840
	tcp_do_segment() at tcp_do_segment+0x2db5/frame 0xfffffe00343b3940
	tcp_input_with_port() at tcp_input_with_port+0x10ec/frame 
0xfffffe00343b3a90
	tcp_input() at tcp_input+0xb/frame 0xfffffe00343b3aa0
	ip_input() at ip_input+0x271/frame 0xfffffe00343b3b00
	netisr_dispatch_src() at netisr_dispatch_src+0xbf/frame 
0xfffffe00343b3b60
	ether_demux() at ether_demux+0x17a/frame 0xfffffe00343b3ba0
	ether_nh_input() at ether_nh_input+0x3b4/frame 0xfffffe00343b3bf0
	netisr_dispatch_src() at netisr_dispatch_src+0xbf/frame 
0xfffffe00343b3c50
	ether_input() at ether_input+0xe9/frame 0xfffffe00343b3cb0
	iflib_rxeof() at iflib_rxeof+0x919/frame 0xfffffe00343b3de0
	_task_fn_rx() at _task_fn_rx+0xce/frame 0xfffffe00343b3e30
	gtaskqueue_run_locked() at gtaskqueue_run_locked+0x1a8/frame 
0xfffffe00343b3ec0
	gtaskqueue_thread_loop() at gtaskqueue_thread_loop+0xd3/frame 
0xfffffe00343b3ef0
	fork_exit() at fork_exit+0x82/frame 0xfffffe00343b3f30
	fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00343b3f30
	--- trap 0xafafafaf, rip = 0xafafafafafafafaf, rsp = 
0xafafafafafafafaf, rbp = 0xafafafafafafafaf ---

—
Kristof