common/read_peer_msg: handle pings in handle_peer_gossip_or_error().

This is a noop for now, since gossipd handles them.  But that
will change in the next patch.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

closingd/Makefile

@@ -47,6 +47,7 @@ CLOSINGD_COMMON_OBJS :=				\
 	common/peer_failed.o			\
 	common/per_peer_state.o			\
 	common/permute_tx.o			\
+	common/ping.o				\
 	common/psbt_open.o			\
 	common/pseudorand.o			\
 	common/read_peer_msg.o			\

common/read_peer_msg.c

@@ -6,6 +6,7 @@
 #include <common/gossip_store.h>
 #include <common/peer_failed.h>
 #include <common/per_peer_state.h>
+#include <common/ping.h>
 #include <common/read_peer_msg.h>
 #include <common/status.h>
 #include <common/wire_error.h>
@@ -156,6 +157,7 @@ bool handle_peer_gossip_or_error(struct per_peer_state *pps,
 {
 	char *err;
 	bool warning;
+	u8 *pong;
 
 #if DEVELOPER
 	/* Any odd-typed unknown message is handled by the caller, so if we
@@ -174,7 +176,11 @@ bool handle_peer_gossip_or_error(struct per_peer_state *pps,
 
 	if (handle_timestamp_filter(pps, msg))
 		return true;
-	else if (is_msg_for_gossipd(msg)) {
+	else if (check_ping_make_pong(NULL, msg, &pong)) {
+		if (pong)
+			sync_crypto_write(pps, take(pong));
+		return true;
+	} else if (is_msg_for_gossipd(msg)) {
 		gossip_rcvd_filter_add(pps->grf, msg);
 		wire_sync_write(pps->gossip_fd, msg);
 		/* wire_sync_write takes, so don't take again. */

common/read_peer_msg.h

@@ -63,7 +63,7 @@ bool is_wrong_channel(const u8 *msg, const struct channel_id *expected,
  *
  * This returns true if it handled the packet: a gossip packet (forwarded
  * to gossipd), or an error packet (causes peer_failed_received_errmsg or
- * ignored).
+ * ignored), or a ping (may reply with pong).
  */
 bool handle_peer_gossip_or_error(struct per_peer_state *pps,
 				 const struct channel_id *channel_id,

openingd/Makefile

@@ -70,6 +70,7 @@ OPENINGD_COMMON_OBJS :=				\
 	common/peer_billboard.o			\
 	common/peer_failed.o			\
 	common/permute_tx.o			\
+	common/ping.o				\
 	common/psbt_internal.o			\
 	common/psbt_open.o			\
 	common/pseudorand.o			\