[zeromq-dev] zmq_forwarder fails when my machine is not on the internet

[Dhammika Pathirana]

>
> I know about this and have reported the issue to the bug tracker.
>
>  There is a problem at least on Linux when the host only has a loopback
>  address configured, getaddrinfo() will not resolve anything. AFAICT this is
>  due to the AI_ADDRCONFIG flag being used when resolving names/addresses.
>
>  > Any thoughts?
>
>  AI_ADDRCONFIG can probably go while we're ignoring IPv6, but this does look
>  like a getaddrinfo() bug to me, since the POSIX wording is:
>
>        "If the AI_ADDRCONFIG flag is specified, IPv4 addresses shall be
>        returned only if an  IPv4  address is configured on the local
>        system,    and IPv6 addresses shall be returned only if an IPv6
>        address is configured on the local
>        system."
>
>  Since when does 127.0.0.1 not count as "an IPv4 address"...?
>


This is actually documented in socket interfaces rfc,
http://tools.ietf.org/rfc/rfc3493.txt

      For example, when using the DNS, a query for AAAA records should
      occur only if the node has at least one IPv6 address configured
      (other than IPv6 loopback) and a query for A records should occur
      only if the node has at least one IPv4 address configured (other
      than the IPv4 loopback).


We can add a check for loopback,

--- a/src/ip.cpp
+++ b/src/ip.cpp
@@ -300,6 +300,17 @@ int zmq::resolve_ip_hostname (sockaddr_storage
*addr_, socklen_t *addr_len_,
     addrinfo *res;
     int rc = getaddrinfo (hostname.c_str (), service.c_str (), &req, &res);
     if (rc) {
+        if (rc == EAI_NONAME) {
+            struct sockaddr_in *ip4_addr = (struct sockaddr_in *)addr_;
+
+            rc = inet_pton (AF_INET, hostname.c_str (), &ip4_addr->sin_addr);
+            if (rc == 1 && ip4_addr->sin_addr.s_addr == htonl
(INADDR_LOOPBACK)) {
+                ip4_addr->sin_family = AF_INET;
+                ip4_addr->sin_port = htons (atoi (service.c_str ()));
+                *addr_len_ = sizeof (struct sockaddr_in);
+                return 0;
+            }
+        }
         errno = EINVAL;
         return -1;
     }