[Bug 264257] [tcp] Panic: Fatal trap 12: page fault while in kernel mode (if_io_tqg_4) - m_copydata ... at /usr/src/sys/kern/uipc_mbuf.c:659

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=264257

--- Comment #37 from Richard Scheffenegger <rscheff@freebsd.org> ---
Can you provide the vmcore (and kernel.debug) files?

Or check 
f 10
p *tp
p *tp->sackhint.nexthole
p tp->snd_una +  tp->t_inpcb->inp_socket->so_snd.sb_ccc
p/x tp->t_flags
p/x tp->t_flags2
p *tp->t_timers

So far, this seems to be the signature:
t_state == 8 (LAST_ACK)
snd_max == snd_una + so_snd.sb_ccc + 2 (! should be one to account for the FIN)
snd_fack < sackhole.end (rescue retransmission - this is new in fbsd13)
t_rxtshift == 6..12 (many retransmission timeouts, indicating the client
disappeared - temporarily)
t_rtseq == snd_una + so_snd.sb_ccc
snd_recover == snd_max (indicating the double-accounting for FIN happend prior
of entering loss recovery, or "many" packets prior of the actual panic)

t_flags = 0x20100274 (TF_CONGRECOVERY, TF_FASTRECOVERY, TF_SACK_PERMIT,
TF_SENTFIN, TF_REQ_SCALE, TF_RCVD_SCALE, TF_NODELAY, TF_ACKNOW)

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