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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2017-01-03 06:31:47 -0800
committerDavid S. Miller <davem@davemloft.net>2017-01-03 11:00:27 -0500
commit7f953ab2ba46e8649537942c0a64668ca2ce5cc5 (patch)
tree7832da3907c92bd7e96b680cefb276e3708d500c /Documentation/networking/packet_mmap.txt
parente7072f6669860c4918ced4acf6a7e482023bd40f (diff)
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 <sowmini.varadhan@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking/packet_mmap.txt')
-rw-r--r--Documentation/networking/packet_mmap.txt9
1 files changed, 7 insertions, 2 deletions
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