On Jun 15, 2014, at 5:23 AM, Fernando Gont wrote:
> I'm trying to send an IPv6 packet with pcap_inject() on the loopback
> interface of a FreeBSD 9.2 system.
>
> What I write with pcap_inect() is the IPv6 packet, preceded with the
> 4-byte AF header (which I set to PF_INET6 (which is 28) in host byte order).
>
> However, pcap_inject() fails with
> "send: Address family not supported by protocol family"
>
> and I also get this message on the console::
> "looutput: af=31 unexpected"
>
> which would seem to indicate that pcap_inject() is overwriting the value
> I set with something else (pseudo_AF_HDRCMPLT?).
It indicates that *some* piece of code is overwriting that value.
However, pcap_inject(), on systems with BPF, is:
static int
pcap_inject_bpf(pcap_t *p, const void *buf, size_t size)
{
int ret;
ret = write(p->fd, buf, size);
#ifdef __APPLE__
a bunch of code only used on OS X/iOS
#endif /* __APPLE__ */
if (ret == -1) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
pcap_strerror(errno));
return (PCAP_ERROR);
}
return (ret);
}
so it's not what's setting pseudo_AF_HDRCMPLT.
The offending code is in bpfwrite():
if (d->bd_hdrcmplt)
dst.sa_family = pseudo_AF_HDRCMPLT;
"dst" is handed to looutput() in sys/net/if_loop.c, which does
/* BPF writes need to be handled specially. */
if (dst->sa_family == AF_UNSPEC)
bcopy(dst->sa_data, &af, sizeof(af));
else
af = dst->sa_family;
The common code for Ethernet sends (ether_output()) explicitly handles both
AF_UNSPEC *and* pseudo_AF_HDRCMPLT; the loopback driver needs to handle it as
well, e.g. either
/* BPF writes need to be handled specially. */
if (dst->sa_family == pseudo_AF_HDRCMPLT)
bcopy(dst->sa_data, &af, sizeof(af));
else
af = dst->sa_family;
or
/* BPF writes need to be handled specially. */
if (dst->sa_family == pseudo_AF_HDRCMPLT || dst->sa_family == AF_UNSPEC)
bcopy(dst->sa_data, &af, sizeof(af));
else
af = dst->sa_family;
As the person who came across this bug, you should file a bug on this; if you
can, CC me on it, or, if not, let me know what bug ID it gets assigned so that
I can try to CC myself on it.
___
tcpdump-workers mailing list
tcpdump-workers@lists.tcpdump.org
https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
