Hello, On Thu, 21 Aug 2014, Johannes Berg wrote: > From: Johannes Berg <johannes.berg@xxxxxxxxx> > > RFC 1122 says that unicast packets encapsulated in broadcast > link-layer packets should be dropped. Implement that, but also > extend it to link-layer multicast packets. > > Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> > --- > net/ipv4/route.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/net/ipv4/route.c b/net/ipv4/route.c > index eaa4b000c7b4..c374fcc73ee0 100644 > --- a/net/ipv4/route.c > +++ b/net/ipv4/route.c > @@ -1710,6 +1710,23 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr, > goto no_route; > } > > + /* RFC 1122 3.3.6: > + * > + * When a host sends a datagram to a link-layer broadcast address, > + * the IP destination address MUST be a legal IP broadcast or IP > + * multicast address. > + * > + * A host SHOULD silently discard a datagram that is received via > + * a link-layer broadcast (see Section 2.4) but does not specify > + * an IP multicast or broadcast destination address. > + * > + * We also do this for link-layer multicast. > + */ > + if ((skb->pkt_type == PACKET_BROADCAST || > + skb->pkt_type == PACKET_MULTICAST) && > + res.type != RTN_BROADCAST) > + goto e_inval; This place is ok for IP context but ip_route_input is also called from ARP context and other places. You are using pkt_type in route.c for first time. At least inet_rtm_getroute() does not set it. You have to audit all call sites, may be skb->protocol check can be needed too, I guess ARP is broken otherwise. And I'm not sure if skb->protocol is actual in ip4ip6_err() after decapsulation. Adding more skb fields to check is risky due to such places. OTOH, the receive routines for protocols like UDP, TCP, SCTP already have pkt_type checks. As result, this is an extra check for them. You should also consider that this change breaks CLUSTERIP which uses multicast link-layer address and local (shared) IP. > if (res.type == RTN_BROADCAST) > goto brd_input; Is this place better, after checking for RTN_BROADCAST? /* ARP link-layer broadcasts are acceptable here */ if ((skb->pkt_type == PACKET_BROADCAST || skb->pkt_type == PACKET_MULTICAST) && skb->protocol == htons(ETH_P_IP)) goto e_inval; Regards -- Julian Anastasov <ja@xxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
