[PATCH net-next v2 31/39] rxrpc: Send jumbo DATA packets

[David Howells <dhowells@redhat.com>]

Send jumbo DATA packets if the path-MTU probing using padded PING ACK
packets shows up sufficient capacity to do so.  This allows larger chunks
of data to be sent without reducing the retryability as the subpackets in a
jumbo packet can also be retransmitted individually.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
---
 net/rxrpc/ar-internal.h | 1 +
 net/rxrpc/call_event.c  | 2 +-
 net/rxrpc/call_object.c | 1 +
 net/rxrpc/input.c       | 3 +++
 4 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index d0d0ab453909..1307749a1a74 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -710,6 +710,7 @@ struct rxrpc_call {
 	u16			tx_backoff;	/* Delay to insert due to Tx failure (ms) */
 	u8			tx_winsize;	/* Maximum size of Tx window */
 #define RXRPC_TX_MAX_WINDOW	128
+	u8			tx_jumbo_max;	/* Maximum subpkts peer will accept */
 	ktime_t			tx_last_sent;	/* Last time a transmission occurred */
 
 	/* Received data tracking */
diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 4390c97e3ba6..39772459426b 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -288,7 +288,7 @@ static void rxrpc_transmit_fresh_data(struct rxrpc_call *call)
 		struct rxrpc_txqueue *tq;
 		struct rxrpc_txbuf *txb;
 		rxrpc_seq_t send_top, seq;
-		int limit = min(space, 1);
+		int limit = min(space, max(call->peer->pmtud_jumbo, 1));
 
 		/* Order send_top before the contents of the new txbufs and
 		 * txqueue pointers
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index bba058055c97..e0644e9a8d21 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -155,6 +155,7 @@ struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp,
 	refcount_set(&call->ref, 1);
 	call->debug_id		= debug_id;
 	call->tx_total_len	= -1;
+	call->tx_jumbo_max	= 1;
 	call->next_rx_timo	= 20 * HZ;
 	call->next_req_timo	= 1 * HZ;
 	call->ackr_window	= 1;
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 1eb9c22aba51..a7a249872a54 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -796,8 +796,11 @@ static void rxrpc_input_ack_trailer(struct rxrpc_call *call, struct sk_buff *skb
 		peer->ackr_adv_pmtud = true;
 	} else {
 		peer->ackr_adv_pmtud = false;
+		capacity = clamp(capacity, 1, jumbo_max);
 	}
 
+	call->tx_jumbo_max = capacity;
+
 	if (wake)
 		wake_up(&call->waitq);
 }