[perfgao]

I hereby granted the copyright of the changes in this pull request
to the authors of this lua-nginx-module project.

ngx_parse_addr_port() returns NGX_DECLINED when the text is not an address; NGX_ERROR only means an allocation failed. ngx_http_lua_ffi_balancer_bind_to_local_addr() only checks for NGX_ERROR:

rc = ngx_parse_addr_port(r->pool, local, (u_char *) addr, addr_len);
if (rc == NGX_ERROR) {

So balancer.bind_to_local_addr("not-an-ip") returns true, and an ngx_addr_t whose sockaddr was never set (it comes from ngx_palloc()) is stored in bp->local. ngx_event_connect_peer() then calls ngx_inet_get_port() and bind() on that pointer:

[lua] balancer_by_lua(nginx.conf:11):4: bind_to_local_addr returned ok=true err=nil while connecting to upstream
[alert] worker process 2710294 exited on signal 11

The Lua wrapper only checks that the argument is a string, so any string that is not an address reaches this path, for example a typo in the configuration or an address taken from request data.

This change treats anything but NGX_OK as an invalid address and keeps the previous bp->local, which is what ngx_stream_lua_ffi_balancer_bind_to_local_addr() already does. With it, the call returns nil, "invalid addr not-an-ip" and the request goes on with the previously bound address.

TEST 6 in t/138-balancer-upstream-bind.t binds 127.0.0.2, then "not-an-ip", and expects the error to be logged and the upstream to see 127.0.0.2. Without the fix the worker crashes and the test fails; with it t/138-balancer-upstream-bind.t passes. Tested against nginx 1.31.1 in an OpenResty build; the function and the test file are the same as on master.