Re: panic: tcp_do_segment: sent too much

> On Jan 13, 2025, at 9:44 AM, Kyle Evans <kevans@FreeBSD.org> wrote:
> 
> Hi,
> 
> I seem to have hit this panic during normal laptop usage with a -CURRENT running at 2832af7b4ea256b18ef4dbf2ff97a50765f0609a:
> 
> panic: tcp_do_segment: sent too much
> cpuid = 5
> time = 1736731772
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe015b74b9b0
> vpanic() at vpanic+0x136/frame 0xfffffe015b74bae0
> panic() at panic+0x43/frame 0xfffffe015b74bb40
> tcp_do_segment() at tcp_do_segment+0x2998/frame 0xfffffe015b74bc20
> tcp_input_with_port() at tcp_input_with_port+0x10f8/frame 0xfffffe015b74bd70
> tcp_input() at tcp_input+0xb/frame 0xfffffe015b74bd80
> ip_input() at ip_input+0x28f/frame 0xfffffe015b74bde0
> swi_net() at swi_net+0x19b/frame 0xfffffe015b74be60
> ithread_loop() at ithread_loop+0x266/frame 0xfffffe015b74bef0
> fork_exit() at fork_exit+0x82/frame 0xfffffe015b74bf30
> fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe015b74bf30
> 
> Doing a little bit of inspection:
> 
> (kgdb) print tp->t_dupacks
> $1 = 1
> (kgdb) print tp->snd_limited
> $6 = 0 '\000'
> (kgdb) p/x tp->t_flags
> $4 = 0x10000264
> (kgdb) print maxseg
> $1 = 1428
> 
> `sent` appears to be optimized out.  As far as I know, I don't hit this one often, but I'm wondering if there's anything else useful I could extract here / if anyone has a theory about what happened.

I also hit this. When I ssh to my dev machine ( 15.0-CURRENT ) and run the build, it happens sometimes. It appears to be easy repeated with busy tcp traffic.

> 
> Thanks,
> 
> Kyle Evans
>