svn commit: r194662 - head/sys/kern

Andre Oppermann andre at
Mon Jun 22 21:46:41 UTC 2009

Author: andre
Date: Mon Jun 22 21:46:40 2009
New Revision: 194662

  In sbappendstream_locked() demote all incoming packet mbufs (and
  chains) to pure data mbufs using m_demote().  This removes the
  packet header and all m_tag information as they are not meaningful
  anymore on a stream socket where mbufs are linked through m->m_next.
  Strictly speaking a packet header can be only ever valid on the first
  mbuf in an m_next chain.
  sbcompress() was doing this already when the mbuf chain layout lent
  itself to it (e.g. header splitting or merge-append), just not
  This frees resources at socket buffer append time instead of at
  sbdrop_internal() time after data has been read from the socket.
  For MAC the per packet information has done its duty and during
  socket buffer appending the policy of the socket itself takes over.
  With the append the packet boundaries disappear naturally and with
  it any context that was based on it.  None of the residual information
  from mbuf headers in the socket buffer on stream sockets was looked at.


Modified: head/sys/kern/uipc_sockbuf.c
--- head/sys/kern/uipc_sockbuf.c	Mon Jun 22 21:42:57 2009	(r194661)
+++ head/sys/kern/uipc_sockbuf.c	Mon Jun 22 21:46:40 2009	(r194662)
@@ -528,6 +528,9 @@ sbappendstream_locked(struct sockbuf *sb
+	/* Remove all packet headers and mbuf tags to get a pure data chain. */
+	m_demote(m, 1);
 	sbcompress(sb, m, sb->sb_mbtail);
 	sb->sb_lastrecord = sb->sb_mb;

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