bcli: don't try asking non-full nodes for blocks.

Suggested-by: @NicolasDorier
Closes: #8078
Signed-off-by: Rusty Russell <[email protected]>
Changelog-Changed: Protocol: we no longer try asking for blocks from bitcoind's peers if they don't store blocks.

Author: rustyrussell

plugins/bcli.c

@@ -626,11 +626,20 @@ static struct command_result *process_getpeerinfo(struct bitcoin_cli *bcli)
 	json_for_each_arr(i, t, toks)
 	{
 		int id;
-		if (json_scan(tmpctx, bcli->output, t, "{id:%}",
-			      JSON_SCAN(json_to_int, &id)) == NULL) {
-			// fixme: future optimization: a) filter for full nodes,
-			// b) sort by last ping
-			tal_arr_expand(&stash->peers, id);
+		u8 *services;
+
+		if (json_scan(tmpctx, bcli->output, t, "{id:%,services:%}",
+			      JSON_SCAN(json_to_int, &id),
+			      JSON_SCAN_TAL(tmpctx, json_tok_bin_from_hex, &services)) == NULL) {
+			/* From bitcoin source:
+			 *  // NODE_NETWORK means that the node is capable of serving the complete block chain. It is currently
+			 *  // set by all Bitcoin Core non pruned nodes, and is unset by SPV clients or other light clients.
+			 * NODE_NETWORK = (1 << 0)
+			 */
+			if (tal_count(services) > 0 && (services[tal_count(services)-1] & (1<<0))) {
+				// fixme: future optimization: sort by last ping
+				tal_arr_expand(&stash->peers, id);
+			}
 		}
 	}
 

tests/test_misc.py

@@ -172,12 +172,15 @@ def mock_getpeerinfo(r, error=False):
             "result": [
                 {
                     "id": 1,
+                    "services": "000000000000040d",
                 },
                 {
                     "id": 2,
+                    "services": "0000000000000001",
                 },
                 {
                     "id": 3,
+                    "services": "0000000000000000",
                 },
             ],
         }
@@ -210,10 +213,10 @@ def mock_getblockfrompeer_inner(r):
     l1.daemon.rpcproxy.mock_rpc("getblockfrompeer", mock_getblockfrompeer())
     l1.start(wait_for_bitcoind_sync=False)
 
-    # check that we fetched a block from a peer (1st peer (from the back) in this case).
+    # check that we fetched a block from a peer (1st peer (from the back) in this case, but not from 3 which isn't a full node).
     pruned_block = bitcoind.rpc.getblockhash(bitcoind.rpc.getblockcount())
     l1.daemon.wait_for_log(f"failed to fetch block {pruned_block} from the bitcoin backend")
-    l1.daemon.wait_for_log(rf"try to fetch block {pruned_block} from peer 3")
+    l1.daemon.wait_for_log(rf"try to fetch block {pruned_block} from peer 2")
     l1.daemon.wait_for_log(rf"Adding block (\d+): {pruned_block}")
 
     # check that we can also fetch from a peer > 1st (from the back).
@@ -222,8 +225,8 @@ def mock_getblockfrompeer_inner(r):
 
     pruned_block = bitcoind.rpc.getblockhash(bitcoind.rpc.getblockcount())
     l1.daemon.wait_for_log(f"failed to fetch block {pruned_block} from the bitcoin backend")
-    l1.daemon.wait_for_log(rf"failed to fetch block {pruned_block} from peer 3")
-    l1.daemon.wait_for_log(rf"try to fetch block {pruned_block} from peer (\d+)")
+    l1.daemon.wait_for_log(rf"failed to fetch block {pruned_block} from peer 2")
+    l1.daemon.wait_for_log(rf"try to fetch block {pruned_block} from peer 1")
     l1.daemon.wait_for_log(rf"Adding block (\d+): {pruned_block}")
 
     # check that we retry if we could not fetch any block