tcpdump mailing list archives

Re: twice past the taps, thence out to net?


From: Eric Dumazet <eric.dumazet () gmail com>
Date: Thu, 15 Dec 2011 19:54:37 +0100

Le jeudi 15 décembre 2011 à 10:32 -0800, Rick Jones a écrit :
More exactly, we call dev_queue_xmit_nit() from dev_hard_start_xmit()
_before_ giving skb to device driver.

If device driver returns NETDEV_TX_BUSY, and a qdisc was setup on the
device, packet is requeued.

Later, when queue is allowed to send again packets, packet is
retransmitted (and traced a second time in dev_queue_xmit_nit())

Is this then an unintended consequence bug, or a known feature?


Its a well known feature, some people attempted to remove it ;)

http://answers.softpicks.net/answers/topic/-PATCH-tcpdump-may-trace-some-outbound-packets-twice--2204640-1.htm



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