Correct mbuf packet header propagation. Previously, packet headers

were sometimes propagated using M_COPY_PKTHDR which actually did
something between a "move" and a  "copy" operation.  This is replaced
by M_MOVE_PKTHDR (which copies the pkthdr contents and "removes" it
from the source mbuf) and m_dup_pkthdr which copies the packet
header contents including any m_tag chain.  This corrects numerous
problems whereby mbuf tags could be lost during packet manipulations.

These changes also introduce arguments to m_tag_copy and m_tag_copy_chain
to specify if the tag copy work should potentially block.  This
introduces an incompatibility with openbsd which we may want to revisit.

Note that move/dup of packet headers does not handle target mbufs
that have a cluster bound to them.  We may want to support this;
for now we watch for it with an assert.

Finally, M_COPYFLAGS was updated to include M_FIRSTFRAG|M_LASTFRAG.

Supported by:	Vernier Networks
Reviewed by:	Robert Watson <rwatson@FreeBSD.org>

1 files changed, 10 insertions, 10 deletions

diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index 9c3affc..7c07931b 100644
--- a/sys/net/if_loop.c
+++ b/sys/net/if_loop.c
@@ -214,19 +214,11 @@ looutput(ifp, m, dst, rt)
 	if (m && m->m_next != NULL && m->m_pkthdr.len < MCLBYTES) {
 		struct mbuf *n;
 
+		/* XXX MT_HEADER should be m->m_type */
 		MGETHDR(n, M_DONTWAIT, MT_HEADER);
 		if (!n)
 			goto contiguousfail;
-		MCLGET(n, M_DONTWAIT);
-		if (! (n->m_flags & M_EXT)) {
-			m_freem(n);
-			goto contiguousfail;
-		}
-
-		m_copydata(m, 0, m->m_pkthdr.len, mtod(n, caddr_t));
-		n->m_pkthdr = m->m_pkthdr;
-		n->m_len = m->m_pkthdr.len;
-		SLIST_INIT(&m->m_pkthdr.tags);
+		M_MOVE_PKTHDR(n, m);
 #ifdef MAC
 		/* 
 		 * XXXMAC: Once we put labels in tags and proper
@@ -235,6 +227,14 @@ looutput(ifp, m, dst, rt)
 		 */
 		m->m_pkthdr.label.l_flags &= ~MAC_FLAG_INITIALIZED;
 #endif
+		MCLGET(n, M_DONTWAIT);
+		if (! (n->m_flags & M_EXT)) {
+			m_freem(n);
+			goto contiguousfail;
+		}
+
+		m_copydata(m, 0, m->m_pkthdr.len, mtod(n, caddr_t));
+		n->m_len = m->m_pkthdr.len;
 		m_freem(m);
 		m = n;
 	}