davide/palladum-lightning
1
0
Fork 0
Code Issues Pull Requests Actions 5 Packages Projects Releases Wiki Activity

chanbackup: unbias our random peer selection.

Browse Source 
We picked one node and iterated.  This means we would only sent to 1,
not 2 nodes if we picked the last (common if there were only a few
peers).  But it also means we would generally send to the same pair of
nodes, which isn't great for redundancy.

Rework to be more random.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2025-05-16 21:34:23 +09:30
parent b7e20b327c
commit 44972b2e15
1 changed files with 40 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
plugins/chanbackup.c
View File

@@ -551,13 +551,47 @@ static struct command_result *after_send_scb_single_fail(struct command *cmd,
return notification_or_hook_done(cmd);
}
static bool already_have_node_id(const struct node_id *ids,
const struct node_id *id)
{
for (size_t i = 0; i < tal_count(ids); i++)
if (node_id_eq(&ids[i], id))
return true;
return false;
}
static const struct node_id *random_peers(const tal_t *ctx,
const struct chanbackup *cb)
{
struct peer_map_iter it;
const struct node_id *peer;
struct node_id *ids = tal_arr(ctx, struct node_id, 0);
/* Simple case: pick all of them */
if (peer_map_count(cb->peers) <= NUM_BACKUP_PEERS) {
for (peer = peer_map_first(cb->peers, &it);
peer;
peer = peer_map_next(cb->peers, &it)) {
tal_arr_expand(&ids, *peer);
}
} else {
while (peer_map_count(cb->peers) < NUM_BACKUP_PEERS) {
peer = peer_map_pick(cb->peers, pseudorand_u64(), &it);
if (already_have_node_id(ids, peer))
continue;
tal_arr_expand(&ids, *peer);
}
}
return ids;
}
static struct command_result *send_to_peers(struct command *cmd)
{
struct out_req *req;
size_t *idx = tal(cmd, size_t);
u8 *serialise_scb, *data;
struct peer_map_iter it;
const struct node_id *peer;
const struct node_id *peers;
struct chanbackup *cb = chanbackup(cmd->plugin);
if (!cb->send_our_peer_backup)
@@ -582,14 +616,13 @@ static struct command_result *send_to_peers(struct command *cmd)
}
serialise_scb = towire_peer_storage(cmd, data);
*idx = 0;
for (peer = peer_map_pick(cb->peers, pseudorand_u64(), &it);
peer;
peer = peer_map_next(cb->peers, &it)) {
peers = random_peers(tmpctx, cb);
*idx = tal_count(peers);
for (size_t i = 0; i < tal_count(peers); i++) {
struct info *info = tal(cmd, struct info);
info->idx = idx;
info->node_id = *peer;
info->node_id = peers[i];
req = jsonrpc_request_start(cmd,
"sendcustommsg",
@@ -599,12 +632,7 @@ static struct command_result *send_to_peers(struct command *cmd)
json_add_node_id(req->js, "node_id", &info->node_id);
json_add_hex_talarr(req->js, "msg", serialise_scb);
(*info->idx)++;
send_outreq(req);
/* Only send to NUM_BACKUP_PEERS for each update */
if (*info->idx == NUM_BACKUP_PEERS)
break;
}
if (*idx == 0)