> > <4>[60392.948306] I[1: ksoftirqd/1: 19] ------------[ cut here
> > ]------------
> > <0>[60392.948334] I[1: ksoftirqd/1: 19] kernel BUG at
> > net/ipv4/tcp_ipv4.c:519!
>
> What the code looks like at line 519 of net/ipv4/tcp_ipv4.c ?
>
> This is not a pristine kernel, anything could be wrong, you might have missed
> some critical backports.
>
I attached that at first mail,
although we added some featre as you said, (about MPTCP)
it looks like clear that the reason for BUG trigger.
> > 370 void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
> > 371 {
> > ...
> > 516 icsk->icsk_rto = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);
> > 517
> > 518 skb = tcp_write_queue_head(sk);
> > 519 BUG_ON(!skb);
> > 520
> > 521 tcp_mstamp_refresh(tp);
> >
> >
> > we know that the line 519 removed on latest state. instead this will be
> > shown to kernel panic.
