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Commit 7f953ab2 authored by Sowmini Varadhan's avatar Sowmini Varadhan Committed by David S. Miller
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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: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e7072f66

Documentation/networking/packet_mmap.txt

+7 −2
Original line number Diff line number Diff line
@@ -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

net/packet/af_packet.c

+30 −9
Original line number Diff line number Diff line
@@ -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();
@@ -2497,6 +2502,13 @@ 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;
@@ -2516,6 +2528,9 @@ 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;
@@ -2525,6 +2540,9 @@ 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;
@@ -4113,11 +4131,6 @@ 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;
@@ -4177,11 +4190,19 @@ 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

		 */

			if (!tx_ring)

			/* Block transmit is not supported yet */

			if (!tx_ring) {

				init_prb_bdqc(po, rb, pg_vec, req_u);

			} else {

				struct tpacket_req3 *req3 = &req_u->req3;



				if (req3->tp_retire_blk_tov ||

				    req3->tp_sizeof_priv ||

				    req3->tp_feature_req_word) {

					err = -EINVAL;

					goto out;

				}

			}

			break;

		default:

			break;