peer_control: don't refer to peer in copy_to_parent_log

Once we rely on the logbook outlasting the peer, we can't refer to the
peer from the logbook function:

Valgrind error file: valgrind-errors.26567
==26567== Invalid read of size 8
==26567==    at 0x126297: copy_to_parent_log (peer_control.c:690)
==26567==    by 0x11C06B: maybe_print (log.c:253)
==26567==    by 0x11C145: logv (log.c:270)
==26567==    by 0x11C448: log_ (log.c:319)
==26567==    by 0x132951: destroy_subd (subd.c:537)
==26567==    by 0x179C19: notify (tal.c:240)
==26567==    by 0x17A0CE: del_tree (tal.c:400)
==26567==    by 0x17A120: del_tree (tal.c:410)
==26567==    by 0x17A4ED: tal_free (tal.c:509)
==26567==    by 0x16DEB5: io_close (io.c:443)
==26567==    by 0x1328BC: sd_msg_read (subd.c:516)
==26567==    by 0x1320AC: read_fds (subd.c:328)
==26567==  Address 0x6cf9ca0 is 48 bytes inside a block of size 216 free'd
==26567==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==26567==    by 0x17A1A9: del_tree (tal.c:421)
==26567==    by 0x17A4ED: tal_free (tal.c:509)
==26567==    by 0x124B6C: delete_peer (peer_control.c:180)
==26567==    by 0x12B369: destroy_uncommitted_channel (peer_control.c:2505)
==26567==    by 0x179C19: notify (tal.c:240)
==26567==    by 0x17A0CE: del_tree (tal.c:400)
==26567==    by 0x17A4ED: tal_free (tal.c:509)
==26567==    by 0x12B31E: opening_channel_errmsg (peer_control.c:2496)
==26567==    by 0x13243A: handle_peer_error (subd.c:407)
==26567==    by 0x1326E4: sd_msg_read (subd.c:472)
==26567==    by 0x1320AC: read_fds (subd.c:328)
==26567==  Block was alloc'd at
==26567==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==26567==    by 0x179C83: allocate (tal.c:250)
==26567==    by 0x17A250: tal_alloc_ (tal.c:448)
==26567==    by 0x124950: new_peer (peer_control.c:151)
==26567==    by 0x12B3EC: new_uncommitted_channel (peer_control.c:2521)
==26567==    by 0x12B5C5: peer_accept_channel (peer_control.c:2569)
==26567==    by 0x126099: peer_sent_nongossip (peer_control.c:641)
==26567==    by 0x113B28: peer_nongossip (gossip_control.c:55)
==26567==    by 0x113D9D: gossip_msg (gossip_control.c:144)
==26567==    by 0x132783: sd_msg_read (subd.c:487)
==26567==    by 0x1320AC: read_fds (subd.c:328)
==26567==    by 0x16D1FE: next_plan (io.c:59)
==26567==

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

lightningd/peer_control.c

@@ -61,7 +61,7 @@ static void copy_to_parent_log(const char *prefix,
 			       const struct timeabs *time,
 			       const char *str,
 			       const u8 *io,
-			       struct peer *peer);
+			       struct log *parent_log);
 static void peer_offer_channel(struct lightningd *ld,
 			       struct funding_channel *fc,
 			       const struct wireaddr *addr,
@@ -113,7 +113,7 @@ struct peer *new_peer(struct lightningd *ld, u64 dbid,
 
 	/* Max 128k per peer. */
 	peer->log_book = new_log_book(128*1024, get_log_level(ld->log_book));
-	set_log_outfn(peer->log_book, copy_to_parent_log, peer);
+	set_log_outfn(peer->log_book, copy_to_parent_log, ld->log);
 	list_add_tail(&ld->peers, &peer->list);
 	tal_add_destructor(peer, destroy_peer);
 	return peer;
@@ -541,14 +541,14 @@ static void copy_to_parent_log(const char *prefix,
 			       const struct timeabs *time,
 			       const char *str,
 			       const u8 *io,
-			       struct peer *peer)
+			       struct log *parent_log)
 {
 	if (level == LOG_IO_IN || level == LOG_IO_OUT)
-		log_io(peer->ld->log, level, prefix, io, tal_len(io));
+		log_io(parent_log, level, prefix, io, tal_len(io));
 	else if (continued)
-		log_add(peer->ld->log, "%s ... %s", prefix, str);
+		log_add(parent_log, "%s ... %s", prefix, str);
 	else
-		log_(peer->ld->log, level, "%s %s", prefix, str);
+		log_(parent_log, level, "%s %s", prefix, str);
 }
 
 struct peer *peer_by_id(struct lightningd *ld, const struct pubkey *id)