tcpdump mailing list archives
Re: TPACKET_V3 timeout bug?
From: Andrew Lunn <andrew () lunn ch>
Date: Sun, 16 Apr 2017 04:10:50 +0200
On Sat, Apr 15, 2017 at 06:45:36PM -0400, Sowmini Varadhan wrote:
On (04/15/17 21:40), Andrew Lunn wrote:In my case, lan3 is up and idle, there are no packets flying around to be captured. So i would expect pcap_next_ex() to exit once a second, with a return value of 0. But it is not, it blocks and stays blocked.:Looking at the libpcap source, the 1000ms timeout is being used as part of the setsockopt(3, SOL_PACKET, PACKET_RX_RING, 0xbe9445c0, 28) call, req.tp_retire_blk_tov is set to the timeoutval.right, aiui, the retire_blk_tov will only kick in if we have at least one frame in a block, but the block is not filled up yet, before the req.tp_retire_blk_tov (1s in your case) expires. If there are 0 frames pending, we should not be waking up the app, so everything seems to be behaving as it should?
Hi Guy You wrote the TPACKET3 set_poll_timeout() handling. Please could you have a look at the thread: https://www.mail-archive.com/netdev () vger kernel org/msg163532.html Do you think this is a kernel problem, libpcap problem, or an application problem? Thanks Andrew _______________________________________________ tcpdump-workers mailing list tcpdump-workers () lists tcpdump org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Current thread:
- Re: TPACKET_V3 timeout bug? Andrew Lunn (Apr 15)
- Re: TPACKET_V3 timeout bug? Guy Harris (Apr 15)
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- Re: TPACKET_V3 timeout bug? Guy Harris (May 02)
- Re: TPACKET_V3 timeout bug? Guy Harris (May 02)
- Message not available
- Message not available
- Message not available
- Re: TPACKET_V3 timeout bug? Guy Harris (May 02)
- Re: TPACKET_V3 timeout bug? Guy Harris (Apr 15)