From 7f953ab2ba46e8649537942c0a64668ca2ce5cc5 Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Tue, 3 Jan 2017 06:31:47 -0800 Subject: af_packet: TX_RING support for TPACKET_V3 Although TPACKET_V3 Rx has some benefits over TPACKET_V2 Rx, *_v3 does not currently have TX_RING support. As a result an application that wants the best perf for Tx and Rx (e.g. to handle request/response transacations) ends up needing 2 sockets, one with *_v2 for Tx and another with *_v3 for Rx. This patch enables TPACKET_V2 compatible Tx features in TPACKET_V3 so that an application can use a single descriptor to get the benefits of _v3 RX_RING and _v2 TX_RING. An application may do a block-send by first filling up multiple frames in the Tx ring and then triggering a transmit. This patch only support fixed size Tx frames for TPACKET_V3, and requires that tp_next_offset must be zero. Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller --- Documentation/networking/packet_mmap.txt | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'Documentation/networking') diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index daa015af16a0..f3b9e507ab05 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -565,7 +565,7 @@ TPACKET_V1 --> TPACKET_V2: (void *)hdr + TPACKET_ALIGN(sizeof(struct tpacket_hdr)) TPACKET_V2 --> TPACKET_V3: - - Flexible buffer implementation: + - Flexible buffer implementation for RX_RING: 1. Blocks can be configured with non-static frame-size 2. Read/poll is at a block-level (as opposed to packet-level) 3. Added poll timeout to avoid indefinite user-space wait @@ -574,7 +574,12 @@ TPACKET_V2 --> TPACKET_V3: 4.1 block::timeout 4.2 tpkt_hdr::sk_rxhash - RX Hash data available in user space - - Currently only RX_RING available + - TX_RING semantics are conceptually similar to TPACKET_V2; + use tpacket3_hdr instead of tpacket2_hdr, and TPACKET3_HDRLEN + instead of TPACKET2_HDRLEN. In the current implementation, + the tp_next_offset field in the tpacket3_hdr MUST be set to + zero, indicating that the ring does not hold variable sized frames. + Packets with non-zero values of tp_next_offset will be dropped. ------------------------------------------------------------------------------- + AF_PACKET fanout mode -- cgit v1.2.3