Date: Wed, 19 Jun 2013 03:08:02 +0000 (UTC) From: Lawrence Stewart <lstewart@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r251984 - head/sys/kern Message-ID: <201306190308.r5J382xs031123@svn.freebsd.org>
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Author: lstewart Date: Wed Jun 19 03:08:01 2013 New Revision: 251984 URL: http://svnweb.freebsd.org/changeset/base/251984 Log: When a previous call to sbsndptr() leaves sb->sb_sndptroff at the start of an mbuf that was fully consumed by the previous call, the mbuf ptr returned by the current call ends up being the previous mbuf in the sb chain to the one that contains the data we want. This does not cause any observable issues because the mbuf copy routines happily walk the mbuf chain to get to the data at the moff offset, which in this case means they effectively skip over the mbuf returned by sbsndptr(). We can't adjust sb->sb_sndptr during the previous call for this case because the next mbuf in the chain may not exist yet. We therefore need to detect the condition and make the adjustment during the current call. Fix by detecting the special case of moff being at the start of the next mbuf in the chain and adjust the required accounting variables accordingly. Reviewed by: andre MFC after: 2 weeks Modified: head/sys/kern/uipc_sockbuf.c Modified: head/sys/kern/uipc_sockbuf.c ============================================================================== --- head/sys/kern/uipc_sockbuf.c Wed Jun 19 02:30:32 2013 (r251983) +++ head/sys/kern/uipc_sockbuf.c Wed Jun 19 03:08:01 2013 (r251984) @@ -942,6 +942,13 @@ sbsndptr(struct sockbuf *sb, u_int off, /* Return closest mbuf in chain for current offset. */ *moff = off - sb->sb_sndptroff; m = ret = sb->sb_sndptr ? sb->sb_sndptr : sb->sb_mb; + if (*moff == m->m_len) { + *moff = 0; + sb->sb_sndptroff += m->m_len; + m = ret = m->m_next; + KASSERT(ret->m_len > 0, + ("mbuf %p in sockbuf %p chain has no valid data", ret, sb)); + } /* Advance by len to be as close as possible for the next transmit. */ for (off = off - sb->sb_sndptroff + len - 1;
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