Am Montag, den 28.04.2014, 13:28 -0400 schrieb Neil Horman: > Rather than 'lingernig' perhaps more exact language to indicate that positive > action is required from the application. Perhaps: > > Packets in the WRONG_FORMAT state block the kernel from sending it and subsequent > packets on the ring. Packet in the WRONG_FORMAT state must be moved to the > AVAILABLE or SEND_REQUEST state (after correcting format errors), so that the > next application call to send() properly transmits the frame. Thanks for the suggestion! I incorporated it into the following updated PACKET_LOSS description: When a malformed packet is encountered on a transmit ring, the default is to reset its tp_status to TP_STATUS_WRONG_FORMAT and abort the transmission immediately. The malformed packet blocks itself and subsequent enqueued packets from being sent. The format error must be fixed, the associated tp_status reset to TP_STATUS_SEND_REQUEST and the transmission process restarted via send(2). However, if PACKET_LOSS is set, any malformed packet will be skipped, its tp_status reset to TP_STATUS_AVAILABLE, and the transmission process continued. IMHO this should go into the PACKET_TX_RING description, but I'd like to defer that until I have a little more spare time on my hands, so I can tackle the entire PACKET_MMAP-related part of the man-page in a single effort. Updated patch follows. Cheers, Carsten diff --git a/man2/getsockopt.2 b/man2/getsockopt.2 index 925fa90..1287efc 100644 --- a/man2/getsockopt.2 +++ b/man2/getsockopt.2 @@ -41,7 +41,7 @@ .\" Modified 1999 by Andi Kleen <ak@xxxxxx>. .\" Removed most stuff because it is in socket.7 now. .\" -.TH GETSOCKOPT 2 2014-01-24 "Linux" "Linux Programmer's Manual" +.TH GETSOCKOPT 2 2014-04-28 "Linux" "Linux Programmer's Manual" .SH NAME getsockopt, setsockopt \- get and set options on sockets .SH SYNOPSIS @@ -205,6 +205,7 @@ system. .BR getprotoent (3), .BR protocols (5), .BR ip (7), +.BR packet (7), .BR socket (7), .BR tcp (7), .BR udp (7), diff --git a/man7/packet.7 b/man7/packet.7 index 11bca48..fc5fdaf 100644 --- a/man7/packet.7 +++ b/man7/packet.7 @@ -9,7 +9,7 @@ .\" .\" $Id: packet.7,v 1.13 2000/08/14 08:03:45 ak Exp $ .\" -.TH PACKET 7 2014-04-24 "Linux" "Linux Programmer's Manual" +.TH PACKET 7 2014-04-28 "Linux" "Linux Programmer's Manual" .SH NAME packet \- packet interface on device level .SH SYNOPSIS @@ -319,14 +319,25 @@ original fanout algorithm selects a backlogged socket, the packet rolls over to the next available one. .TP .BR PACKET_LOSS " (with " PACKET_TX_RING ) -When a malformed packet is encountered on a transmit ring, the default is to -set its status to +When a malformed packet is encountered on a transmit ring, the default is +to reset its +.I tp_status +to .BR TP_STATUS_WRONG_FORMAT -and abort the transmission immediately (it and following packets are left -lingering on the ring). +and abort the transmission immediately. +The malformed packet blocks itself and subsequent enqueued packets from +being sent. +The format error must be fixed, the associated +.I tp_status +reset to +.BR TP_STATUS_SEND_REQUEST +and the transmission process restarted via +.BR send (2) . However, if .BR PACKET_LOSS -is set, any malformed packet will be skipped, its status reset to +is set, any malformed packet will be skipped, its +.I tp_status +reset to .BR TP_STATUS_AVAILABLE , and the transmission process continued. .TP @@ -360,15 +371,21 @@ Packet socket and application communicate the head and tail of the ring through the .I tp_status field. -The packet socket owns all slots with status +The packet socket owns all slots with +.I tp_status +equal to .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 has the +During normal operation, the new +.I tp_status +value has at least the .BR TP_STATUS_USER bit set to signal that a 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 +ownership of the slot back to the socket by setting +.I tp_status +equal to .BR TP_STATUS_KERNEL . Packet sockets implement multiple variants of the packet ring. The implementation details are described in @@ -407,9 +424,13 @@ Create a memory-mapped ring buffer for packet transmission. This option is similar to .BR PACKET_RX_RING and takes the same arguments. -The application writes packets into slots with status +The application writes packets into slots with +.I tp_status +equal to .BR TP_STATUS_AVAILABLE -and schedules them for transmission by changing the status to +and schedules them for transmission by changing +.I tp_status +to .BR TP_STATUS_SEND_REQUEST . When packets are ready to be transmitted, the application calls .BR send (2) @@ -424,7 +445,9 @@ If an address is passed using or .BR sendmsg (2), then that overrides the socket default. -On successful transmission, the socket resets the slot to +On successful transmission, the socket resets +.I tp_status +to .BR TP_STATUS_AVAILABLE . It immediately aborts the transmission on error unless .BR PACKET_LOSS @@ -633,6 +656,11 @@ The .I <linux/if_ether.h> include file for physical layer protocols. -The example source file +The Linux kernel source tree. +.IR /Documentation/networking/filter.txt +describes how to apply Berkeley Packet Filters to packet sockets. .IR /tools/testing/selftests/net/psock_tpacket.c -in the Linux kernel source tree. +contains example source code for all available versions of +.BR PACKET_RX_RING +and +.BR PACKET_TX_RING . -- 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
