commit e9b26ae5264e28aea08896b29044a670e864ac14
author Roman Arutyunyan <arut@nginx.com> Tue Dec 11 19:41:22 2018 +0300
committer Roman Arutyunyan <arut@nginx.com> Tue Dec 11 19:41:22 2018 +0300
tree 9bbdafc1a1104465b3cd428d554338d71dfff68c
parent 20ebf1513db474a295a36bbf60173edb2a851d1b

Resolver: report SRV resolve failure if all A resolves failed.

Previously, if an SRV record was successfully resolved, but all of its A
records failed to resolve, NXDOMAIN was returned to the caller, which is
considered a successful resolve rather than an error.  This could result in
losing the result of a previous successful resolve by the caller.

Now NXDOMAIN is only returned if at least one A resolve completed with this
code.  Otherwise the error state of the first A resolve is returned.

src/core/ngx_resolver.c

diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
index 5d7fe31..593645d 100644
--- a/src/core/ngx_resolver.c
+++ b/src/core/ngx_resolver.c
@@ -4266,7 +4266,15 @@
     }
 
     if (naddrs == 0) {
-        ctx->state = NGX_RESOLVE_NXDOMAIN;
+        ctx->state = srvs[0].state;
+
+        for (i = 0; i < nsrvs; i++) {
+            if (srvs[i].state == NGX_RESOLVE_NXDOMAIN) {
+                ctx->state = NGX_RESOLVE_NXDOMAIN;
+                break;
+            }
+        }
+
         ctx->valid = ngx_time() + (r->valid ? r->valid : 10);
 
         ctx->handler(ctx);