On 04/22/2014 08:36 PM, Willem de Bruijn wrote: > On Tue, Apr 22, 2014 at 2:23 PM, Michael Kerrisk (man-pages) > <mtk.manpages@xxxxxxxxx> wrote: >> Hi Daniel, Willem, >> >> >> Daniel, your patch (dbb4f7516b) added the text on PACKET_LOSS. >> Could you comment on the patch below please? > > Carsten is correct. I made a mistake in that explanation, accidentally > inverting the branch. My apologies and thanks for following up with a > replacement text, Carsten. That looks good to me. @Willem: thanks for the quick response. That helps so much. @Carsten: I've applied your patch, but I have a question. You wrote: [[ However if .BR PACKET_LOSS is set, malformed packets will be skipped, their status reset to .BR TP_STATUS_AVAILABLE ]] What does "their" in "their status" refer to? Cheers, Michael >> On 04/22/2014 06:01 PM, Carsten Andrich wrote: >>> Hey there, >>> >>> I stumbled upon an error in packet.7 regarding the meaning of the >>> PACKET_LOSS socket option. According to the current git version of >>> linux-man setting PACKET_LOSS causes malformed packets to *not* be >>> silently dropped. >>> >>> However it is the other way round. If PACKET_LOSS is *not* set, >>> malformed packets will be marked TP_STATUS_WRONG_FORMAT and the >>> transmission process aborted, leaving untransmitted packets in the ring. >>> If it *is* set, malformed packets will be silently skipped, their status >>> set to TP_STATUS_AVAILABLE and the transmission process continued with >>> the following packet. >>> >>> This behaviour can be clearly seen in net/packet/af_packet.c: >>> http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/net/packet/af_packet.c#n2300 >>> >>> The value accompanying TP_PACKET_LOSS translates into po->tp_loss: >>> http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/net/packet/af_packet.c#n3304 >>> >>> I inverted the meaning of PACKET_LOSS and clarified the description in >>> the attached patch. >> >> diff --git a/man7/packet.7 b/man7/packet.7 >> index d8257f9..5085814 100644 >> --- a/man7/packet.7 >> +++ b/man7/packet.7 >> @@ -319,9 +319,15 @@ original fanout algorithm selects a backlogged socket, the packet >> rolls over to the next available one. >> .TP >> .BR PACKET_LOSS " (with " PACKET_TX_RING ) >> -If set, do not silently drop a packet on transmission error, but >> -return it with status set to >> -.BR TP_STATUS_WRONG_FORMAT . >> +When a malformed packet is encountered on a transmit ring, the default is to >> +set its status to >> +.BR TP_STATUS_WRONG_FORMAT >> +and abort the transmission immediately (it and following packets are left >> +lingering on the ring). However if >> +.BR PACKET_LOSS >> +is set, malformed packets will be skipped, their status reset to >> +.BR TP_STATUS_AVAILABLE >> +and the transmission process continued. >> .TP >> .BR PACKET_RESERVE " (with " PACKET_RX_RING ) >> By default, a packet receive ring writes packets immediately following the >> @@ -419,7 +425,7 @@ or >> then that overrides the socket default. >> On successful transmission, the socket resets the slot to >> .BR TP_STATUS_AVAILABLE . >> -It discards packets silently on error unless >> +It immediately aborts the transmission on error unless >> .BR PACKET_LOSS >> is set. >> .TP >> >> >> -- >> Michael Kerrisk >> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ >> Linux/UNIX System Programming Training: http://man7.org/training/ > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
