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ipv4: add option to drop gratuitous ARP packets

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In certain 802.11 wireless deployments, there will be ARP proxies
that use knowledge of the network to correctly answer requests.
To prevent gratuitous ARP frames on the shared medium from being
a problem, on such deployments wireless needs to drop them.

Enable this by providing an option called "drop_gratuitous_arp".

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Johannes Berg 2016-02-04 13:31:18 +01:00 committed by David S. Miller
parent 12b74dfadb
commit 97daf33145
4 changed files with 17 additions and 0 deletions
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6
Documentation/networking/ip-sysctl.txt
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@ -1223,6 +1223,12 @@ drop_unicast_in_l2_multicast - BOOLEAN
1122, but is disabled by default for compatibility reasons. 1122, but is disabled by default for compatibility reasons.
Default: off (0) Default: off (0)
drop_gratuitous_arp - BOOLEAN
Drop all gratuitous ARP frames, for example if there's a known
good ARP proxy on the network and such frames need not be used
(or in the case of 802.11, must not be used to prevent attacks.)
Default: off (0)
tag - INTEGER tag - INTEGER
Allows you to write a number, which can be used as required. Allows you to write a number, which can be used as required.

1
include/uapi/linux/ip.h
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@ -166,6 +166,7 @@ enum
IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL, IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL,
IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN, IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST, IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
IPV4_DEVCONF_DROP_GRATUITOUS_ARP,
__IPV4_DEVCONF_MAX __IPV4_DEVCONF_MAX
}; };

8
net/ipv4/arp.c
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@ -735,6 +735,14 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
(!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip))) (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
goto out; goto out;
/*
* For some 802.11 wireless deployments (and possibly other networks),
* there will be an ARP proxy and gratuitous ARP frames are attacks
* and thus should not be accepted.
*/
if (sip == tip && IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP))
goto out;
/* /*
* Special case: We must set Frame Relay source Q.922 address * Special case: We must set Frame Relay source Q.922 address
*/ */

2
net/ipv4/devinet.c
View File

@ -2185,6 +2185,8 @@ static struct devinet_sysctl_table {
"igmpv3_unsolicited_report_interval"), "igmpv3_unsolicited_report_interval"),
DEVINET_SYSCTL_RW_ENTRY(IGNORE_ROUTES_WITH_LINKDOWN, DEVINET_SYSCTL_RW_ENTRY(IGNORE_ROUTES_WITH_LINKDOWN,
"ignore_routes_with_linkdown"), "ignore_routes_with_linkdown"),
DEVINET_SYSCTL_RW_ENTRY(DROP_GRATUITOUS_ARP,
"drop_gratuitous_arp"),
DEVINET_SYSCTL_FLUSHING_ENTRY(NOXFRM, "disable_xfrm"), DEVINET_SYSCTL_FLUSHING_ENTRY(NOXFRM, "disable_xfrm"),
DEVINET_SYSCTL_FLUSHING_ENTRY(NOPOLICY, "disable_policy"), DEVINET_SYSCTL_FLUSHING_ENTRY(NOPOLICY, "disable_policy"),