topology_hiding: do not warn per request on a non-local send socket

[Lt-Flash]

What

Two problems in topo_no_dlg_seq_handling(), in the branch that restores the send socket recorded in the encoded topology-hiding state: a log line that fires on every sequential request in any multi-node deployment, and — in the same branch — the unusable socket being assigned anyway, clearing whatever the script had already chosen.

1. A WARN per sequential request

When dialog-less topology hiding decodes the state of a sequential request, it looks up the socket the state was created on:

sock = grep_sock_info(&host, (unsigned short)port, proto);
if (!sock) {
    LM_WARN("non-local socket <%.*s>...ignoring\n", bind_buf.len, bind_buf.s);
}

A node not owning that socket is routine, not exceptional: any anycast or load-balanced tier can land a sequential request on a different node than the one that handled the initial request, and a node whose listening set has simply changed hits it too. The result is one WARN per sequential request, per call — on a busy presence deployment that is the bulk of the log.

Dropped to LM_DBG. The R-URI has already been restored by this point, so the request still routes; only the send socket is affected.

2. The failed lookup was not actually ignored

The message says "ignoring", but the assignment sat outside the check:

if (!sock) {
    LM_WARN(... "ignoring" ...);
}
msg->force_send_socket = sock;      /* <-- runs even when sock == NULL */

So on the failure path it stored NULL — wiping any socket the script had already selected (e.g. an earlier force_send_socket() in the route) rather than leaving it alone. The fix only assigns when a local socket was actually found:

if (!sock) {
    LM_DBG("non-local socket <%.*s> - leaving the send socket to the caller\n", ...);
} else {
    msg->force_send_socket = sock;
}

Impact

Log volume on multi-node topology-hiding deployments, and — for scripts that set a send socket before topology_hiding_match() — a silently discarded choice on any request whose state came from another node.