diff options
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 7 | ||||
| -rw-r--r-- | include/uapi/linux/ip.h | 1 | ||||
| -rw-r--r-- | net/ipv4/devinet.c | 2 | ||||
| -rw-r--r-- | net/ipv4/ip_input.c | 25 |
4 files changed, 34 insertions, 1 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 73b36d7c7b0d..d5910d63214d 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -1216,6 +1216,13 @@ promote_secondaries - BOOLEAN promote a corresponding secondary IP address instead of removing all the corresponding secondary IP addresses. +drop_unicast_in_l2_multicast - BOOLEAN + Drop any unicast IP packets that are received in link-layer + multicast (or broadcast) frames. + This behavior (for multicast) is actually a SHOULD in RFC + 1122, but is disabled by default for compatibility reasons. + Default: off (0) + tag - INTEGER Allows you to write a number, which can be used as required. diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h index 08f894d2ddbd..584834f7e95c 100644 --- a/include/uapi/linux/ip.h +++ b/include/uapi/linux/ip.h @@ -165,6 +165,7 @@ enum IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL, IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL, IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN, + IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST, __IPV4_DEVCONF_MAX }; diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index cebd9d31e65a..dbbab28a52a4 100644 --- a/net/ipv4/devinet.c +++ b/net/ipv4/devinet.c @@ -2192,6 +2192,8 @@ static struct devinet_sysctl_table { "promote_secondaries"), DEVINET_SYSCTL_FLUSHING_ENTRY(ROUTE_LOCALNET, "route_localnet"), + DEVINET_SYSCTL_FLUSHING_ENTRY(DROP_UNICAST_IN_L2_MULTICAST, + "drop_unicast_in_l2_multicast"), }, }; diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c index d77eb0c3b684..852002f64c68 100644 --- a/net/ipv4/ip_input.c +++ b/net/ipv4/ip_input.c @@ -362,8 +362,31 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb) rt = skb_rtable(skb); if (rt->rt_type == RTN_MULTICAST) { IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INMCAST, skb->len); - } else if (rt->rt_type == RTN_BROADCAST) + } else if (rt->rt_type == RTN_BROADCAST) { IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INBCAST, skb->len); + } else if (skb->pkt_type == PACKET_BROADCAST || + skb->pkt_type == PACKET_MULTICAST) { + struct in_device *in_dev = __in_dev_get_rcu(skb->dev); + + /* 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. + * + * This doesn't explicitly say L2 *broadcast*, but broadcast is + * in a way a form of multicast and the most common use case for + * this is 802.11 protecting against cross-station spoofing (the + * so-called "hole-196" attack) so do it for both. + */ + if (in_dev && + IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) + goto drop; + } return dst_input(skb); |