Date: Tue, 28 Aug 2007 16:00:26 +1200 From: Andrew Thompson <thompsa@FreeBSD.org> To: FreeBSD Current <current@freebsd.org> Subject: multicast packets from bpf Message-ID: <20070828040026.GB42201@heff.fud.org.nz>
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Hi,
At the moment packets injected via bpf do not get the M_BCAST or M_MCAST
flags set. One consequence of this is that it messes up broadcasting
from if_bridge which assumes these flags are correct, using dhcpd on a
bridge interface is one way to trigger it.
Attached is a patch (bpf_mcast.diff) that fixes this up. There is some
concern about having bpf inspecting the protocol headers but i seems
unavoidable in order to determine if its multicast. tap(4) was also
thought to have this problem but it turned out not to since it passes
the frames to ether_input.
The other way is for the bridge to recheck for multicast destinations
for locally generated packets (bridge_bpfmcast.diff), but this is less
desirable.
Andrew
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Index: bpf.c
===================================================================
RCS file: /home/ncvs/src/sys/net/bpf.c,v
retrieving revision 1.180
diff -u -p -r1.180 bpf.c
--- bpf.c 6 Aug 2007 14:26:00 -0000 1.180
+++ bpf.c 28 Aug 2007 01:34:27 -0000
@@ -599,6 +599,7 @@ bpfwrite(struct cdev *dev, struct uio *u
struct ifnet *ifp;
struct mbuf *m, *mc;
struct sockaddr dst;
+ struct ether_header *eh;
int error, hlen;
if (d->bd_bif == NULL)
@@ -620,6 +621,20 @@ bpfwrite(struct cdev *dev, struct uio *u
if (error)
return (error);
+ /* Check for multicast destination */
+ switch (d->bd_bif->bif_dlt) {
+ case DLT_EN10MB:
+ eh = mtod(m, struct ether_header *);
+ if (ETHER_IS_MULTICAST(eh->ether_dhost)) {
+ if (bcmp(ifp->if_broadcastaddr, eh->ether_dhost,
+ ETHER_ADDR_LEN) == 0)
+ m->m_flags |= M_BCAST;
+ else
+ m->m_flags |= M_MCAST;
+ }
+ break;
+ }
+
if (d->bd_hdrcmplt)
dst.sa_family = pseudo_AF_HDRCMPLT;
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Index: if_bridge.c
===================================================================
RCS file: /home/ncvs/src/sys/net/if_bridge.c,v
retrieving revision 1.102
diff -u -p -r1.102 if_bridge.c
--- if_bridge.c 1 Aug 2007 00:33:52 -0000 1.102
+++ if_bridge.c 14 Aug 2007 02:11:16 -0000
@@ -1852,9 +1852,16 @@ bridge_start(struct ifnet *ifp)
dst_if = NULL;
BRIDGE_LOCK(sc);
- if ((m->m_flags & (M_BCAST|M_MCAST)) == 0) {
+ if (ETHER_IS_MULTICAST(eh->ether_dhost))
+ /*
+ * XXX bpf injected packets do not have M_MCAST or
+ * M_BCAST set, bridge_broadcast() makes assumptions
+ * based on this.
+ */
+ if ((m->m_flags & (M_BCAST|M_MCAST)) == 0)
+ m->m_flags |= M_MCAST;
+ else
dst_if = bridge_rtlookup(sc, eh->ether_dhost, 1);
- }
if (dst_if == NULL)
bridge_broadcast(sc, ifp, m, 0);
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