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.varad...@oracle.com>
---
v2: sanity checks on tp_next_offset and corresponding Doc updates
as suggested by Willem de Bruijn
Documentation/networking/packet_mmap.txt | 9 +++++++--
net/packet/af_packet.c | 27 +++++++++++++++++++--------
2 files changed, 26 insertions(+), 10 deletions(-)
diff --git a/Documentation/networking/packet_mmap.txt
b/Documentation/networking/packet_mmap.txt
index daa015a..f3b9e50 100644
--- a/Documentation/networking/packet_mmap.txt
+++ b/Documentation/networking/packet_mmap.txt
@@ -565,7 +565,7 @@ where 'tpacket_version' can be TPACKET_V1 (default),
TPACKET_V2, TPACKET_V3.
(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 @@ where 'tpacket_version' can be TPACKET_V1 (default),
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
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 89f2e8c..513f52b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -409,6 +409,9 @@ static void __packet_set_status(struct packet_sock *po,
void *frame, int status)
flush_dcache_page(pgv_to_page(&h.h2->tp_status));
break;
case TPACKET_V3:
+ h.h3->tp_status = status;
+ flush_dcache_page(pgv_to_page(&h.h3->tp_status));
+ break;
default:
WARN(1, "TPACKET version not supported.\n");
BUG();
@@ -432,6 +435,8 @@ static int __packet_get_status(struct packet_sock *po, void
*frame)
flush_dcache_page(pgv_to_page(&h.h2->tp_status));
return h.h2->tp_status;
case TPACKET_V3:
+ flush_dcache_page(pgv_to_page(&h.h3->tp_status));
+ return h.h3->tp_status;
default:
WARN(1, "TPACKET version not supported.\n");
BUG();
@@ -2500,6 +2505,13 @@ static int tpacket_parse_header(struct packet_sock *po,
void *frame,
ph.raw = frame;
switch (po->tp_version) {
+ case TPACKET_V3:
+ if (ph.h3->tp_next_offset != 0) {
+ pr_warn_once("variable sized slot not supported");
+ return -EINVAL;
+ }
+ tp_len = ph.h3->tp_len;
+ break;
case TPACKET_V2:
tp_len = ph.h2->tp_len;
break;
@@ -2519,6 +2531,9 @@ static int tpacket_parse_header(struct packet_sock *po,
void *frame,
off_max = po->tx_ring.frame_size - tp_len;
if (po->sk.sk_type == SOCK_DGRAM) {
switch (po->tp_version) {
+ case TPACKET_V3:
+ off = ph.h3->tp_net;
+ break;
case TPACKET_V2:
off = ph.h2->tp_net;
break;
@@ -2528,6 +2543,9 @@ static int tpacket_parse_header(struct packet_sock *po,
void *frame,
}
} else {
switch (po->tp_version) {
+ case TPACKET_V3:
+ off = ph.h3->tp_mac;
+ break;
case TPACKET_V2:
off = ph.h2->tp_mac;
break;
@@ -4116,11 +4134,6 @@ static int packet_set_ring(struct sock *sk, union
tpacket_req_u *req_u,
struct tpacket_req *req = &req_u->req;
lock_sock(sk);
- /* Opening a Tx-ring is NOT supported in TPACKET_V3 */
- if (!closing && tx_ring && (po->tp_version > TPACKET_V2)) {
- net_warn_ratelimited("Tx-ring is not supported.\n");
- goto out;
- }
rb = tx_ring ? &po->tx_ring : &po->rx_ring;
rb_queue = tx_ring ? &sk->sk_write_queue : &sk->sk_receive_queue;
@@ -4180,9 +4193,7 @@ static int packet_set_ring(struct sock *sk, union
tpacket_req_u *req_u,
goto out;
switch (po->tp_version) {
case TPACKET_V3:
- /* Transmit path is not supported. We checked
- * it above but just being paranoid
- */
+ /* Block transmit is not supported yet */
if (!tx_ring)
init_prb_bdqc(po, rb, pg_vec, req_u);
break;
--
1.7.1
