svn commit: r300764 - head/sys/netinet

[Bjoern A. Zeeb]

> On 26 May 2016, at 18:35 , John Baldwin <jhb at FreeBSD.org> wrote:
> 
> Author: jhb
> Date: Thu May 26 18:35:37 2016
> New Revision: 300764
> URL: https://svnweb.freebsd.org/changeset/base/300764
> 
> Log:
>  Don't reuse the source mbuf in tcp_respond() if it is not writable.
> 
>  Not all mbufs passed up from device drivers are M_WRITABLE().  In
>  particular, the Chelsio T4/T5 driver uses a feature called "buffer packing"
>  to receive multiple frames in a single receive buffer.  The mbufs for
>  these frames all share the same external storage so are treated as
>  read-only by the rest of the stack when multiple frames are in flight.
>  Previously tcp_respond() would blindly overwrite read-only mbufs when
>  INVARIANTS was disabled or panic with an assertion failure if INVARIANTS
>  was enabled.  Note that the new case is a bit of a mix of the two other
>  cases in tcp_respond().  The TCP and IP headers must be copied explicitly
>  into the new mbuf instead of being inherited (similar to the m == NULL
>  case), but the addresses and ports must be swapped in the reply (similar
>  to the m != NULL case).

Is the same true for ICMP(v6) replies?

/bz