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Add support for fragmenting ipv4 packets.

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The packet filter may reassemble the ip fragments and return a packet that is
larger than the MTU of the sending interface. There is no check for DF or icmp
replies as we can only get a large packet to fragment by reassembling a
previous fragment, and this only happens after a call to pfil(9).

Obtained from:	OpenBSD (mostly)
Glanced at by:	mlaier
MFC after:	1 month
This commit is contained in:
Andrew Thompson 2006-04-29 05:37:25 +00:00
parent de4bee5922
commit 7f87a57ca3
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=158140
1 changed files with 85 additions and 7 deletions
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92
sys/net/if_bridge.c
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@ -263,6 +263,8 @@ static int bridge_ip_checkbasic(struct mbuf **mp);
# ifdef INET6
static int bridge_ip6_checkbasic(struct mbuf **mp);
# endif /* INET6 */
static int bridge_fragment(struct ifnet *, struct mbuf *,
struct ether_header *, int, struct llc *);
SYSCTL_DECL(_net_link);
SYSCTL_NODE(_net_link, IFT_BRIDGE, bridge, CTLFLAG_RW, 0, "Bridge");
@ -1497,13 +1499,22 @@ bridge_stop(struct ifnet *ifp, int disable)
__inline void
bridge_enqueue(struct bridge_softc *sc, struct ifnet *dst_ifp, struct mbuf *m)
{
int len, err;
int len, err = 0;
short mflags;
struct mbuf *m0;
len = m->m_pkthdr.len;
mflags = m->m_flags;
IFQ_ENQUEUE(&dst_ifp->if_snd, m, err);
/* We may be sending a framgment so traverse the mbuf */
for (; m; m = m0) {
m0 = m->m_nextpkt;
m->m_nextpkt = NULL;
if (err == 0)
IFQ_ENQUEUE(&dst_ifp->if_snd, m, err);
}
if (err == 0) {
sc->sc_ifp->if_opackets++;
@ -2761,13 +2772,24 @@ bridge_pfil(struct mbuf **mp, struct ifnet *bifp, struct ifnet *ifp, int dir)
error = pfil_run_hooks(&inet_pfil_hook, mp, bifp,
dir, NULL);
/* Restore ip and the fields ntohs()'d. */
if (*mp != NULL && error == 0) {
ip = mtod(*mp, struct ip *);
ip->ip_len = htons(ip->ip_len);
ip->ip_off = htons(ip->ip_off);
if (*mp == NULL || error != 0) /* filter may consume */
break;
/* check if we need to fragment the packet */
if (pfil_member && ifp != NULL && dir == PFIL_OUT) {
i = (*mp)->m_pkthdr.len;
if (i > ifp->if_mtu) {
error = bridge_fragment(ifp, *mp, &eh2, snap,
&llc1);
return (error);
}
}
/* Restore ip and the fields ntohs()'d. */
ip = mtod(*mp, struct ip *);
ip->ip_len = htons(ip->ip_len);
ip->ip_off = htons(ip->ip_off);
break;
# ifdef INET6
case ETHERTYPE_IPV6 :
@ -2979,3 +3001,59 @@ bridge_ip6_checkbasic(struct mbuf **mp)
return -1;
}
# endif /* INET6 */
/*
* bridge_fragment:
*
* Return a fragmented mbuf chain.
*/
static int
bridge_fragment(struct ifnet *ifp, struct mbuf *m, struct ether_header *eh,
int snap, struct llc *llc)
{
struct mbuf *m0;
struct ip *ip;
int error = -1;
if (m->m_len < sizeof(struct ip) &&
(m = m_pullup(m, sizeof(struct ip))) == NULL)
goto out;
ip = mtod(m, struct ip *);
error = ip_fragment(ip, &m, ifp->if_mtu, ifp->if_hwassist,
CSUM_DELAY_IP);
if (error)
goto out;
/* walk the chain and re-add the Ethernet header */
for (m0 = m; m0; m0 = m0->m_nextpkt) {
if (error == 0) {
if (snap) {
M_PREPEND(m0, sizeof(struct llc), M_DONTWAIT);
if (m0 == NULL) {
error = ENOBUFS;
continue;
}
bcopy(llc, mtod(m0, caddr_t),
sizeof(struct llc));
}
M_PREPEND(m0, ETHER_HDR_LEN, M_DONTWAIT);
if (m0 == NULL) {
error = ENOBUFS;
continue;
}
bcopy(eh, mtod(m0, caddr_t), ETHER_HDR_LEN);
} else
m_freem(m);
}
if (error == 0)
ipstat.ips_fragmented++;
return (error);
out:
if (m != NULL)
m_freem(m);
return (error);
}