On Fri, Feb 18, 2011 at 07:26:18PM +0800, Shan Wei wrote:
> Jiri Bohac wrote, at 02/18/2011 07:12 AM:
> > commit 5fa782c2f5ef6c2e4f04d3e228412c9b4a4c8809 re-worked the
> > handling of unknown parameters. sctp_init_cause_fixed() can now
> > return -ENOSPC if there is not enough tailroom in the error
> > chunk skb. When this happens, the error header is not appended to
> > the error chunk. In that case, the payload of the unknown parameter
> > should not be appended either.
> >
> > Signed-off-by: Jiri Bohac <jbohac@xxxxxxx>
>
> For this case, there is no more tailroom in skb
not always true:
both sctp_init_cause_fixed() and sctp_addto_chunk_fixed() get
passesd WORD_ROUND(ntohs(param.p->length) as the paylen/len
parameter.
sctp_init_cause_fixed() does:
len = sizeof(sctp_errhdr_t) + paylen;
if (skb_tailroom(chunk->skb) < len)
return -ENOSPC;
if paylen is only slightly smaller than the tailroom (by less
than sizeof(sctp_errhdr_t) bytes), -ENOSPEC will be returned and
the header will not be appended to the error chunk.
But later sctp_addto_chunk_fixed() does this check:
if (skb_tailroom(chunk->skb) >= len)
which will pass and the unknown parameter value will be appended
to the error chunk without the error header.
> we send incomplete INIT-ACK chunk. With your patch, this chunk also
> can't info the sender of INIT Chunk which parameter is not unrecognized.
> So maybe this handle is not perfect.
The logic of not reporting unknown parameters for which we don't
have space in the pre-allocated buffer remains unchanged.
--
Jiri Bohac <jbohac@xxxxxxx>
SUSE Labs, SUSE CZ
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