lightningd: fix scb remote_to_self_delay information.

This was changing all the time when I tried to make
autogenerate-rpc-examples.py reproducible.  Turns out it was being
corrupted (it does suspicious things with pointers); rather than try
to diagnose it, I simply rewrote the code to create it only when we
need it.

```
Valgrind error file: valgrind-errors.34506
==34506== Uninitialised byte(s) found during client check request
==34506==    at 0x241732: memcheck_ (mem.h:247)
==34506==    by 0x2417BC: towire (towire.c:17)
==34506==    by 0x24185C: towire_u16 (towire.c:28)
==34506==    by 0x20C8E4: towire_tlv_scb_tlvs_remote_to_self_delay (scb_wiregen.c:213)
==34506==    by 0x240E78: towire_tlv (tlvstream.c:342)
==34506==    by 0x20C99F: towire_tlv_scb_tlvs (scb_wiregen.c:234)
==34506==    by 0x20C298: towire_modern_scb_chan (scb_wiregen.c:89)
==34506==    by 0x1A6CF3: json_add_scb (peer_control.c:2488)
==34506==    by 0x1A6E0C: json_staticbackup (peer_control.c:2519)
==34506==    by 0x177E3F: command_exec (jsonrpc.c:799)
==34506==    by 0x1785AE: rpc_command_hook_final (jsonrpc.c:945)
==34506==    by 0x1BEC2D: plugin_hook_call_next (plugin_hook.c:199)
==34506==  Address 0x1ffeffe736 is on thread 1's stack
==34506==  in frame #2, created by towire_u16 (towire.c:26)
==34506== 
{
   <insert_a_suppression_name_here>
   Memcheck:User
   fun:memcheck_
   fun:towire
   fun:towire_u16
   fun:towire_tlv_scb_tlvs_remote_to_self_delay
   fun:towire_tlv
   fun:towire_tlv_scb_tlvs
   fun:towire_modern_scb_chan
   fun:json_add_scb
   fun:json_staticbackup
   fun:command_exec
   fun:rpc_command_hook_final
   fun:plugin_hook_call_next
}
==34506== Uninitialised byte(s) found during client check request
==34506==    at 0x241732: memcheck_ (mem.h:247)
==34506==    by 0x2417BC: towire (towire.c:17)
==34506==    by 0x240EF0: towire_tlv (tlvstream.c:354)
==34506==    by 0x20C99F: towire_tlv_scb_tlvs (scb_wiregen.c:234)
==34506==    by 0x20C298: towire_modern_scb_chan (scb_wiregen.c:89)
==34506==    by 0x1A6CF3: json_add_scb (peer_control.c:2488)
==34506==    by 0x1A6E0C: json_staticbackup (peer_control.c:2519)
==34506==    by 0x177E3F: command_exec (jsonrpc.c:799)
==34506==    by 0x1785AE: rpc_command_hook_final (jsonrpc.c:945)
==34506==    by 0x1BEC2D: plugin_hook_call_next (plugin_hook.c:199)
==34506==    by 0x1BEBA8: plugin_hook_callback (plugin_hook.c:186)
==34506==    by 0x1B771E: plugin_response_handle (plugin.c:705)
==34506==  Address 0x7bd1d08 is 40 bytes inside a block of size 42 alloc'd
==34506==    at 0x484DCD3: realloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==34506==    by 0x3C8614: tal_resize_ (tal.c:755)
==34506==    by 0x2417A2: towire (towire.c:14)
==34506==    by 0x24185C: towire_u16 (towire.c:28)
==34506==    by 0x20C8E4: towire_tlv_scb_tlvs_remote_to_self_delay (scb_wiregen.c:213)
==34506==    by 0x240E78: towire_tlv (tlvstream.c:342)
==34506==    by 0x20C99F: towire_tlv_scb_tlvs (scb_wiregen.c:234)
==34506==    by 0x20C298: towire_modern_scb_chan (scb_wiregen.c:89)
==34506==    by 0x1A6CF3: json_add_scb (peer_control.c:2488)
==34506==    by 0x1A6E0C: json_staticbackup (peer_control.c:2519)
==34506==    by 0x177E3F: command_exec (jsonrpc.c:799)
==34506==    by 0x1785AE: rpc_command_hook_final (jsonrpc.c:945)
==34506==
```

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

Author: rustyrussell

lightningd/channel.c

@@ -343,7 +343,6 @@ struct channel *new_unsaved_channel(struct peer *peer,
 	channel->openchannel_signed_cmd = NULL;
 	channel->state = DUALOPEND_OPEN_INIT;
 	channel->owner = NULL;
-	channel->scb = NULL;
 	channel->reestablished = false;
 	memset(&channel->billboard, 0, sizeof(channel->billboard));
 	channel->billboard.transient = tal_fmt(channel, "%s",
@@ -578,30 +577,6 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->billboard.transient = tal_strdup(channel, transient_billboard);
 	channel->channel_info = *channel_info;
 
-	/* If it's a unix domain socket connection, we don't save it */
-	if (peer->addr.itype == ADDR_INTERNAL_WIREADDR) {
-		channel->scb = tal(channel, struct modern_scb_chan);
-		channel->scb->id = dbid;
-		/* More useful to have last_known_addr, if avail */
-		if (peer->last_known_addr)
-			channel->scb->addr = *peer->last_known_addr;
-		channel->scb->addr = peer->addr.u.wireaddr.wireaddr;
-		channel->scb->node_id = peer->id;
-		channel->scb->funding = *funding;
-		channel->scb->cid = *cid;
-		channel->scb->funding_sats = funding_sats;
-		channel->scb->type = channel_type_dup(channel->scb, type);
-
-		struct tlv_scb_tlvs *scb_tlvs = tlv_scb_tlvs_new(channel);
-		scb_tlvs->shachain = &channel->their_shachain.chain;
-		scb_tlvs->basepoints = &channel->channel_info.theirbase;
-		scb_tlvs->opener = &channel->opener;
-		scb_tlvs->remote_to_self_delay = &channel->channel_info.their_config.to_self_delay;
-
-		channel->scb->tlvs = scb_tlvs;
-	} else
-		channel->scb = NULL;
-
 	if (!log) {
 		channel->log = new_logger(channel,
 					  peer->ld->log_book,

lightningd/channel.h

@@ -343,10 +343,6 @@ struct channel {
 	/* Lease commited max part per thousandth channel fee (ppm * 1000) */
 	u16 lease_chan_max_ppt;
 
-	/* `Channel-shell` of this channel
-	 * (Minimum information required to backup this channel). */
-	struct modern_scb_chan *scb;
-
 	/* Do we allow the peer to set any fee it wants? */
 	bool ignore_fee_limits;
 

lightningd/dual_open_control.c

@@ -1467,28 +1467,9 @@ wallet_commit_channel(struct lightningd *ld,
 					     &commitment_feerate);
 	channel->min_possible_feerate = commitment_feerate;
 	channel->max_possible_feerate = commitment_feerate;
-	if (channel->peer->addr.itype == ADDR_INTERNAL_WIREADDR) {
-		channel->scb = tal(channel, struct modern_scb_chan);
-		channel->scb->id = channel->dbid;
-		channel->scb->addr = channel->peer->addr.u.wireaddr.wireaddr;
-		channel->scb->node_id = channel->peer->id;
-		channel->scb->funding = *funding;
-		channel->scb->cid = channel->cid;
-		channel->scb->funding_sats = total_funding;
-
-		struct tlv_scb_tlvs *scb_tlvs = tlv_scb_tlvs_new(channel);
-		scb_tlvs->shachain = &channel->their_shachain.chain;
-		scb_tlvs->basepoints = &channel_info->theirbase;
-		scb_tlvs->opener = &channel->opener;
-		scb_tlvs->remote_to_self_delay = &channel_info->their_config.to_self_delay;
-
-		channel->scb->tlvs = scb_tlvs;
-	} else
-		channel->scb = NULL;
 
 	tal_free(channel->type);
 	channel->type = channel_type_dup(channel, type);
-	channel->scb->type = channel_type_dup(channel->scb, type);
 
 	if (our_upfront_shutdown_script)
 		channel->shutdown_scriptpubkey[LOCAL]

lightningd/peer_control.c

@@ -2480,15 +2480,35 @@ static void json_add_scb(struct command *cmd,
 			 struct json_stream *response,
 			 struct channel *c)
 {
-	u8 *scb = tal_arr(cmd, u8, 0);
+	u8 *scb_wire = tal_arr(cmd, u8, 0);
+	struct modern_scb_chan *scb;
 
-	/* Update shachain & basepoints in SCB. */
-	c->scb->tlvs->shachain = &c->their_shachain.chain;
-	c->scb->tlvs->basepoints = &c->channel_info.theirbase;
-	towire_modern_scb_chan(&scb, c->scb);
+	/* Don't do scb for unix domain sockets. */
+	if (c->peer->addr.itype != ADDR_INTERNAL_WIREADDR)
+		return;
+
+	scb = tal(tmpctx, struct modern_scb_chan);
+	scb->id = c->dbid;
+	/* More useful to have last_known_addr, if avail */
+	if (c->peer->last_known_addr)
+		scb->addr = *c->peer->last_known_addr;
+	else
+		scb->addr = c->peer->addr.u.wireaddr.wireaddr;
+	scb->node_id = c->peer->id;
+	scb->funding = c->funding;
+	scb->cid = c->cid;
+	scb->funding_sats = c->funding_sats;
+	scb->type = channel_type_dup(scb, c->type);
+
+	scb->tlvs = tlv_scb_tlvs_new(scb);
+	scb->tlvs->shachain = &c->their_shachain.chain;
+	scb->tlvs->basepoints = &c->channel_info.theirbase;
+	scb->tlvs->opener = &c->opener;
+	scb->tlvs->remote_to_self_delay = &c->channel_info.their_config.to_self_delay;
+
+	towire_modern_scb_chan(&scb_wire, scb);
 
-	json_add_hex_talarr(response, fieldname,
-			    scb);
+	json_add_hex_talarr(response, fieldname, scb_wire);
 }
 
 /* This will return a SCB for all the channels currently loaded
@@ -2513,8 +2533,7 @@ static struct command_result *json_staticbackup(struct command *cmd,
 	     peer = peer_node_id_map_next(cmd->ld->peers, &it)) {
 		struct channel *channel;
 		list_for_each(&peer->channels, channel, list){
-			/* cppcheck-suppress uninitvar - false positive on channel */
-			if (!channel->scb)
+			if (channel_state_uncommitted(channel->state))
 				continue;
 			json_add_scb(cmd, NULL, response, channel);
 		}

lightningd/test/run-invoice-select-inchan.c

@@ -144,6 +144,10 @@ const char *channel_state_name(const struct channel *channel UNNEEDED)
 /* Generated stub for channel_state_str */
 const char *channel_state_str(enum channel_state state UNNEEDED)
 { fprintf(stderr, "channel_state_str called!\n"); abort(); }
+/* Generated stub for channel_type_dup */
+struct channel_type *channel_type_dup(const tal_t *ctx UNNEEDED,
+				      const struct channel_type *t UNNEEDED)
+{ fprintf(stderr, "channel_type_dup called!\n"); abort(); }
 /* Generated stub for channel_type_has */
 bool channel_type_has(const struct channel_type *type UNNEEDED, int feature UNNEEDED)
 { fprintf(stderr, "channel_type_has called!\n"); abort(); }
@@ -969,6 +973,9 @@ void subd_send_fd(struct subd *sd UNNEEDED, int fd UNNEEDED)
 /* Generated stub for subd_send_msg */
 void subd_send_msg(struct subd *sd UNNEEDED, const u8 *msg_out UNNEEDED)
 { fprintf(stderr, "subd_send_msg called!\n"); abort(); }
+/* Generated stub for tlv_scb_tlvs_new */
+struct tlv_scb_tlvs *tlv_scb_tlvs_new(const tal_t *ctx UNNEEDED)
+{ fprintf(stderr, "tlv_scb_tlvs_new called!\n"); abort(); }
 /* Generated stub for towire_bigsize */
 void towire_bigsize(u8 **pptr UNNEEDED, const bigsize_t val UNNEEDED)
 { fprintf(stderr, "towire_bigsize called!\n"); abort(); }