[PATCH net-next 07/21] rxrpc: Do lazy DF flag resetting

[David Howells]

Don't reset the DF flag after transmission, but rather set it when needed
since it should be a fast op now that we call IP directly.

This includes turning it off for RESPONSE packets and, for the moment, ACK
packets.  In future, we will need to turn it on for ACK packets used to do
path MTU discovery.

Signed-off-by: David Howells <dhowells at redhat.com>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: "David S. Miller" <davem at davemloft.net>
cc: Eric Dumazet <edumazet at google.com>
cc: Jakub Kicinski <kuba at kernel.org>
cc: Paolo Abeni <pabeni at redhat.com>
cc: linux-afs at lists.infradead.org
cc: netdev at vger.kernel.org
---
 net/rxrpc/output.c | 4 ++--
 net/rxrpc/rxkad.c  | 1 -
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 1e039b6f4494..8aa8ba32eacc 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -231,6 +231,7 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 	txb->ack.previousPacket	= htonl(call->rx_highest_seq);
 
 	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, len);
+	rxrpc_local_dont_fragment(conn->local, false);
 	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
 	call->peer->last_tx_at = ktime_get_seconds();
 	if (ret < 0) {
@@ -406,6 +407,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 	 * think it's small enough */
 	if (txb->len >= call->peer->maxdata)
 		goto send_fragmentable;
+	rxrpc_local_dont_fragment(conn->local, true);
 
 	txb->wire.flags = txb->flags & RXRPC_TXBUF_WIRE_FLAGS;
 	txb->last_sent = ktime_get_real();
@@ -492,8 +494,6 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_frag);
 		ret = do_udp_sendmsg(conn->local->socket, &msg, len);
 		conn->peer->last_tx_at = ktime_get_seconds();
-
-		rxrpc_local_dont_fragment(conn->local, true);
 		break;
 
 	default:
diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index 28c9ce763be4..e451ac90bfee 100644
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -726,7 +726,6 @@ static int rxkad_send_response(struct rxrpc_connection *conn,
 
 	rxrpc_local_dont_fragment(conn->local, false);
 	ret = kernel_sendmsg(conn->local->socket, &msg, iov, 3, len);
-	rxrpc_local_dont_fragment(conn->local, true);
 	if (ret < 0) {
 		trace_rxrpc_tx_fail(conn->debug_id, serial, ret,
 				    rxrpc_tx_point_rxkad_response);