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

[Martin Sustrik]

Mato,

What do you think about the patch below? Should I commit it to the trunk?

Martin

Dhammika Pathirana wrote:
>> 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;
>      }
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