ai_protocol

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 <larsi@gnus.org>
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

Re: ai_protocol

[Paul Eggert]

[-- Attachment #1: Type: text/plain, Size: 70 bytes --]

Thanks, good catch. I installed the attached, which I think fixes it.

[-- Attachment #2: 0001-Don-t-use-only-last-protocol-from-getaddrinfo.txt --]
[-- Type: text/plain, Size: 7297 bytes --]

From 86ea531030c7b79195abc51d7401f6c6836b2a06 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 23 May 2016 08:56:42 -0700
Subject: [PATCH] =?UTF-8?q?Don=E2=80=99t=20use=20only=20last=20protocol=20?=
 =?UTF-8?q?from=20getaddrinfo?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Problem reported by Ken Brown in:
http://lists.gnu.org/archive/html/emacs-devel/2016-05/msg00483.html
* src/process.c (conv_addrinfo_to_lisp): New function.
(connect_network_socket): Arg is now a list of addrinfos, not
merely IP addresses.  All uses changed.  Use protocol from
each addrinfo.
(Fmake_network_process): Accumulate protocols into addrinfos
rather than just using the last one found.
(check_for_dns): Accumulate protocols here, too.
* src/process.h (struct Lisp_Process): Remove ai_protocol;
no longer needed.
---
 src/process.c | 63 ++++++++++++++++++++++++++++++-----------------------------
 src/process.h |  2 --
 2 files changed, 32 insertions(+), 33 deletions(-)

diff --git a/src/process.c b/src/process.c
index d4bd19a..9ca3e594 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2343,6 +2343,16 @@ conv_sockaddr_to_lisp (struct sockaddr *sa, ptrdiff_t len)
   return address;
 }
 
+/* Convert an internal struct addrinfo to a Lisp object.  */
+
+static Lisp_Object
+conv_addrinfo_to_lisp (struct addrinfo *res)
+{
+  Lisp_Object protocol = make_number (res->ai_protocol);
+  eassert (XINT (protocol) == res->ai_protocol);
+  return Fcons (protocol, conv_sockaddr_to_lisp (res->ai_addr, res->ai_addrlen));
+}
+
 
 /* Get family and required size for sockaddr structure to hold ADDRESS.  */
 
@@ -3097,14 +3107,13 @@ finish_after_tls_connection (Lisp_Object proc)
 #endif
 
 static void
-connect_network_socket (Lisp_Object proc, Lisp_Object ip_addresses,
+connect_network_socket (Lisp_Object proc, Lisp_Object addrinfos,
                         Lisp_Object use_external_socket_p)
 {
   ptrdiff_t count = SPECPDL_INDEX ();
   ptrdiff_t count1;
   int s = -1, outch, inch;
   int xerrno = 0;
-  Lisp_Object ip_address;
   int family;
   struct sockaddr *sa = NULL;
   int ret;
@@ -3126,10 +3135,12 @@ connect_network_socket (Lisp_Object proc, Lisp_Object ip_addresses,
   count1 = SPECPDL_INDEX ();
   s = -1;
 
-  while (!NILP (ip_addresses))
+  while (!NILP (addrinfos))
     {
-      ip_address = XCAR (ip_addresses);
-      ip_addresses = XCDR (ip_addresses);
+      Lisp_Object addrinfo = XCAR (addrinfos);
+      addrinfos = XCDR (addrinfos);
+      int protocol = XINT (XCAR (addrinfo));
+      Lisp_Object ip_address = XCDR (addrinfo);
 
 #ifdef WINDOWSNT
     retry_connect:
@@ -3147,7 +3158,7 @@ connect_network_socket (Lisp_Object proc, Lisp_Object ip_addresses,
 	  int socktype = p->socktype | SOCK_CLOEXEC;
 	  if (p->is_non_blocking_client)
 	    socktype |= SOCK_NONBLOCK;
-	  s = socket (family, socktype, p->ai_protocol);
+	  s = socket (family, socktype, protocol);
 	  if (s < 0)
 	    {
 	      xerrno = errno;
@@ -3624,10 +3635,10 @@ usage: (make-network-process &rest ARGS)  */)
   Lisp_Object tem;
   Lisp_Object name, buffer, host, service, address;
   Lisp_Object filter, sentinel, use_external_socket_p;
-  Lisp_Object ip_addresses = Qnil;
+  Lisp_Object addrinfos = Qnil;
   int socktype;
   int family = -1;
-  int ai_protocol = 0;
+  enum { any_protocol = 0 };
 #ifdef HAVE_GETADDRINFO_A
   struct gaicb *dns_request = NULL;
 #endif
@@ -3680,7 +3691,7 @@ usage: (make-network-process &rest ARGS)  */)
       if (!get_lisp_to_sockaddr_size (address, &family))
 	error ("Malformed :address");
 
-      ip_addresses = list1 (address);
+      addrinfos = list1 (Fcons (make_number (any_protocol), address));
       goto open_socket;
     }
 
@@ -3744,7 +3755,7 @@ usage: (make-network-process &rest ARGS)  */)
       CHECK_STRING (service);
       if (sizeof address_un.sun_path <= SBYTES (service))
 	error ("Service name too long");
-      ip_addresses = list1 (service);
+      addrinfos = list1 (Fcons (make_number (any_protocol), service));
       goto open_socket;
     }
 #endif
@@ -3845,14 +3856,9 @@ usage: (make-network-process &rest ARGS)  */)
       immediate_quit = 0;
 
       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;
-	}
+	addrinfos = Fcons (conv_addrinfo_to_lisp (lres), addrinfos);
 
-      ip_addresses = Fnreverse (ip_addresses);
+      addrinfos = Fnreverse (addrinfos);
 
       freeaddrinfo (res);
 
@@ -3919,7 +3925,6 @@ usage: (make-network-process &rest ARGS)  */)
   p->is_server = false;
   p->port = port;
   p->socktype = socktype;
-  p->ai_protocol = ai_protocol;
 #ifdef HAVE_GETADDRINFO_A
   p->dns_request = NULL;
 #endif
@@ -3952,7 +3957,7 @@ usage: (make-network-process &rest ARGS)  */)
 #ifdef HAVE_GETADDRINFO_A
   /* With async address resolution, the list of addresses is empty, so
      postpone connecting to the server. */
-  if (!p->is_server && NILP (ip_addresses))
+  if (!p->is_server && NILP (addrinfos))
     {
       p->dns_request = dns_request;
       p->status = Qconnect;
@@ -3960,7 +3965,7 @@ usage: (make-network-process &rest ARGS)  */)
     }
 #endif
 
-  connect_network_socket (proc, ip_addresses, use_external_socket_p);
+  connect_network_socket (proc, addrinfos, use_external_socket_p);
   return proc;
 }
 
@@ -4647,7 +4652,7 @@ static Lisp_Object
 check_for_dns (Lisp_Object proc)
 {
   struct Lisp_Process *p = XPROCESS (proc);
-  Lisp_Object ip_addresses = Qnil;
+  Lisp_Object addrinfos = Qnil;
 
   /* Sanity check. */
   if (! p->dns_request)
@@ -4663,13 +4668,9 @@ check_for_dns (Lisp_Object proc)
       struct addrinfo *res;
 
       for (res = p->dns_request->ar_result; res; res = res->ai_next)
-	{
-	  ip_addresses = Fcons (conv_sockaddr_to_lisp
-				(res->ai_addr, res->ai_addrlen),
-				ip_addresses);
-	}
+	addrinfos = Fcons (conv_addrinfo_to_lisp (res), addrinfos);
 
-      ip_addresses = Fnreverse (ip_addresses);
+      addrinfos = Fnreverse (addrinfos);
     }
   /* The DNS lookup failed. */
   else if (EQ (p->status, Qconnect))
@@ -4688,7 +4689,7 @@ check_for_dns (Lisp_Object proc)
   if (!EQ (p->status, Qconnect))
     return Qnil;
 
-  return ip_addresses;
+  return addrinfos;
 }
 
 #endif /* HAVE_GETADDRINFO_A */
@@ -4871,9 +4872,9 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 		/* Check for pending DNS requests. */
 		if (p->dns_request)
 		  {
-		    Lisp_Object ip_addresses = check_for_dns (aproc);
-		    if (!NILP (ip_addresses) && !EQ (ip_addresses, Qt))
-		      connect_network_socket (aproc, ip_addresses, Qnil);
+		    Lisp_Object addrinfos = check_for_dns (aproc);
+		    if (!NILP (addrinfos) && !EQ (addrinfos, Qt))
+		      connect_network_socket (aproc, addrinfos, Qnil);
 		    else
 		      retry_for_async = true;
 		  }
diff --git a/src/process.h b/src/process.h
index 20593f5..a5f690d 100644
--- a/src/process.h
+++ b/src/process.h
@@ -173,8 +173,6 @@ struct Lisp_Process
     int port;
     /* The socket type. */
     int socktype;
-    /* The socket protocol. */
-    int ai_protocol;
 
 #ifdef HAVE_GETADDRINFO_A
     /* Whether the socket is waiting for response from an asynchronous
-- 
2.5.5