ipv4: allow warming up the ARP cache with request type gratuitous ARP (6d955180) · Commits · 戴 / test

If the per device ARP_ACCEPT option is enable, currently we only allow creating new ARP cache entries for response type gratuitous ARP. Allowing gratuitous ARP to create new ARP entries (not only to update existing ones) is useful when we want to avoid unnecessary delays for the first packet of a stream. This patch allows request type gratuitous ARP to create new ARP cache entries as well. This is useful when we want to populate the ARP cache entries for a large number of hosts on the same LAN. Signed-off-by:

Octavian Purdila <opurdila@ixiacom.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

+12 −3

Original line number	Diff line number	Diff line
		@@ -852,9 +852,18 @@ arp_notify - BOOLEAN
		or hardware address changes.

		arp_accept - BOOLEAN
		Define behavior when gratuitous arp replies are received:
		0 - drop gratuitous arp frames
		1 - accept gratuitous arp frames
		Define behavior for gratuitous ARP frames who's IP is not
		already present in the ARP table:
		0 - don't create new entries in the ARP table
		1 - create new entries in the ARP table

		Both replies and requests type gratuitous arp will trigger the
		ARP table to be updated, if this setting is on.

		If the ARP table already contains the IP address of the
		gratuitous arp frame, the arp table will be updated regardless
		if this setting is on or off.


		app_solicit - INTEGER
		The maximum number of probes to send to the user space ARP daemon

net/ipv4/arp.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -907,7 +907,8 @@ static int arp_process(struct sk_buff *skb)
		devices (strip is candidate)
		*/
		if (n == NULL &&
		arp->ar_op == htons(ARPOP_REPLY) &&
		(arp->ar_op == htons(ARPOP_REPLY) \|\|
		(arp->ar_op == htons(ARPOP_REQUEST) && tip == sip)) &&
		inet_addr_type(net, sip) == RTN_UNICAST)
		n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
		}

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