Date: Fri, 29 Oct 2010 09:42:09 -0400 From: George Neville-Neil <gnn@neville-neil.com> To: arch@freebsd.org Subject: RFC: ARP Packet Queues Message-ID: <D92A9067-7305-42B6-8D15-D0A49A0542A4@neville-neil.com>
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Howdy, Please review the following patch against HEAD: http://people.freebsd.org/~gnn/head-arpqueue.diff =20 This patch makes two changes to the ARP code: 1) It adds a sysctl configurable queue of packets that are held until an = ARP reply is received or timed out. net.link.ether.inet.maxhold Having the queue addresses a problem in modern systems where programs = that use connectionless=20 protocols for communication will suffer from dropping many packets when = they start up or when an ARP entry moves. 2) Makes the time we wait for an arp reply configurable via another = sysctl. net.link.ether.inet.wait The old, pre 8.0, ARP code would run the timer once per second. The new ARP code sets a timeout of 20 seconds on each entry. Neither value was = specified in RFC 826. As a matter of fact, RFC 826 had this to say about = timeouts: "It may be desirable to have table aging and/or timeouts. The implementation of these is outside the scope of this protocol." This new code does not change the default value of either the arpqueue = (which was always 1 packet) nor does it change the new value of the ARP down = timeout. I have a different patch for 7, which I will propose after I can get = this in to HEAD and MFC'd to 8. Best, George
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