ai_protocol

[Ken Brown]

I'm puzzled by the handling of ai_protocol in process.c, starting with 
the following commit:

commit e09c0972c350e9411683b509414fc598cbf387d3
Author: Lars Ingebrigtsen <address@hidden>
Date:   Thu Jan 28 23:50:47 2016 +0100

     Refactor make_network_process

     * src/process.c (set_network_socket_coding_system)
     (connect_network_socket): Refactor out of
     make_network_process to allow calling connect_network_socket
     asynchronously.
     (Fmake_network_process): Do nothing but parsing the parameters
     and name resolution, leaving the connection to
     connect_network_socket.

Before that commit, the calls to 'socket' in Fmake_network_connection 
looked like this, in a loop through the structures returned by getaddrinfo:

  for (lres = res; lres; lres = lres->ai_next)
    {
[...]
      s = socket (lres->ai_family, lres->ai_socktype | SOCK_CLOEXEC,
                  lres->ai_protocol);

After that commit, there is a loop in Fmake_network_connection that 
builds a list 'ip_addresses', as follows:

      for (lres = res; lres; lres = lres->ai_next)
        {
          ip_addresses = Fcons (conv_sockaddr_to_lisp
                                (lres->ai_addr, lres->ai_addrlen),
                                ip_addresses);
          ai_protocol = lres->ai_protocol;

Notice that the variable ai_protocol is reset on each iteration of the 
loop.  Later we have

  p->ai_protocol = ai_protocol;

so that the process's ai_protocol is set to whatever value was assigned 
on the last iteration of the loop.

Then connect_network_socket is called.  It loops through ip_addresses 
and does

      s = socket (family, p->socktype | SOCK_CLOEXEC, p->ai_protocol);


always using the fixed value p->ai_protocol as third argument.  This 
seems wrong, but maybe I'm missing something.

Ken