Willem, Daniel, Carsten, Neil, All of you have submitted patches in the recent past for packet.7, and are presumably somewhat knowledgeable. Could one or more of your Ack (or, if needed, improve) Stefan's proposed change? Thanks, Michael On Tue, Feb 25, 2014 at 10:24 PM, Stefan Puiu <stefan.puiu@xxxxxxxxx> wrote: > [re-sending since the original message was bounced back, something > about HTML subpart] > > Hi, > > I'm playing with the PACKET_RX_RING option to packet sockets and I > noticed that the status field from the tpacket_hdr structures inside > the mmaped buffer is actually a bit mask. I'm testing with 4Gbps > traffic rates and sometimes I get status=5. I'm using Ubuntu 12.04 > with a 3.8.0-29 kernel, and at least from the code (I got it using > "sudo apt-get source linux-image-$(uname -r)") it seems the 5 means > TP_STATUS_USER | TP_STATUS_LOSING. The 3.8.0 kernel code has this line > in tpacket_rcv(): > > /* > * LOSING will be reported till you read the stats, > * because it's COR - Clear On Read. > * Anyways, moving it for V1/V2 only as V3 doesn't need this > * at packet level. > */ > if (po->stats.tp_drops) > status |= TP_STATUS_LOSING; > > Also, in some source code example I found using google > (http://www.google.ro/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&ved=0CEIQFjAE&url=http%3A%2F%2Fstuff.mit.edu%2Fafs%2Fsipb%2Fcontrib%2Flinux%2Ftools%2Ftesting%2Fselftests%2Fnet%2Fpsock_fanout.c&ei=lM8MU5yhB-iK7Aan7IGgAQ&usg=AFQjCNFtZBHSWgzHZkV3LNfLOSSTq0pV4Q&sig2=razCT0kUDv2-BIm_8gTE5g&bvm=bv.61725948,d.ZGU), > the status is checked like this: > > while (header->tp_status & TP_STATUS_USER && count < RING_NUM_FRAMES) { > [...] > > I haven't yet figured out how TP_STATUS_LOSING works, but I think it > would be worthwhile to at least document that the status is a bit mask > and not a value - that's what the patch at the end does. > > Michael, maybe you can Cc somebody more knowledgeable on this to > confirm? IIRC there were some message exchanges on this on the list > recently... > > > diff --git a/man7/packet.7 b/man7/packet.7 > index 1d3f222..6bac465 100644 > --- a/man7/packet.7 > +++ b/man7/packet.7 > @@ -353,9 +353,9 @@ The packet socket owns all slots with status > .BR TP_STATUS_KERNEL . > After filling a slot, it changes the status of the slot to transfer > ownership to the application. > -During normal operation, the new status is > -.BR TP_STATUS_USER , > -to signal that a correctly received packet has been stored. > +During normal operation, the new status has the > +.BR TP_STATUS_USER > +bit set to signal that a correctly received packet has been stored. > When the application has finished processing a packet, it transfers > ownership of the slot back to the socket by setting the status to > -- > 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 -- 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
