From 063277c5ecd82551b2bf1409d1583edc7c0fcaad Mon Sep 17 00:00:00 2001
From: Robert Pluim <rpluim@gmail.com>
Date: Thu, 7 Nov 2019 16:16:39 +0100
Subject: [PATCH] Ensure building and running on non-IPv6 capable hosts works

* src/process.c (Fmake_network_process) [AF_INET6]: Only build ::1
localhost when IPv6 is supported.
(Fnetwork_lookup_address_info) [AF_INET6]: Move check for Qipv6 inside
ifdef, since its definition depends on AF_INET6.  Don't return IPv6
addresses when they're not supported.

* test/src/process-tests.el (lookup-family-specification,
lookup-google): Only do IPv6 lookup if IPv6 is supported.
---
 src/process.c             | 24 ++++++++++++++++--------
 test/src/process-tests.el | 11 ++++++-----
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/src/process.c b/src/process.c
index 1f959e39607..8aa4811f7ed 100644
--- a/src/process.c
+++ b/src/process.c
@@ -4015,9 +4015,11 @@ usage: (make-network-process &rest ARGS)  */)
       if (family != AF_LOCAL)
 #endif
         {
+#ifdef AF_INET6
         if (family == AF_INET6)
           host = build_string ("::1");
         else
+#endif
           host = build_string ("127.0.0.1");
         }
     }
@@ -4027,9 +4029,11 @@ usage: (make-network-process &rest ARGS)  */)
         {
 	/* Depending on setup, "localhost" may map to different IPv4 and/or
 	   IPv6 addresses, so it's better to be explicit (Bug#6781).  */
+#ifdef AF_INET6
         if (family == AF_INET6)
           host = build_string ("::1");
         else
+#endif
           host = build_string ("127.0.0.1");
         }
       CHECK_STRING (host);
@@ -4622,7 +4626,8 @@ DEFUN ("network-lookup-address-info", Fnetwork_lookup_address_info,
 Optional parameter FAMILY controls whether to look up IPv4 or IPv6
 addresses.  The default of nil means both, symbol `ipv4' means IPv4
 only, symbol `ipv6' means IPv6 only.  Returns a list of addresses, or
-nil if none were found.  Each address is a vector of integers.  */)
+nil if none were found.  Each address is a vector of integers, as per
+the description of ADDRESS in `make-network-process'.  */)
      (Lisp_Object name, Lisp_Object family)
 {
   Lisp_Object addresses = Qnil;
@@ -4636,12 +4641,9 @@ nil if none were found.  Each address is a vector of integers.  */)
     hints.ai_family = AF_UNSPEC;
   else if (EQ (family, Qipv4))
     hints.ai_family = AF_INET;
-  else if (EQ (family, Qipv6))
 #ifdef AF_INET6
+  else if (EQ (family, Qipv6))
     hints.ai_family = AF_INET6;
-#else
-  /* If we don't support IPv6, querying will never work anyway */
-    return addresses;
 #endif
   else
     error ("Unsupported lookup type");
@@ -4653,9 +4655,15 @@ nil if none were found.  Each address is a vector of integers.  */)
   else
     {
       for (lres = res; lres; lres = lres->ai_next)
-	addresses = Fcons (conv_sockaddr_to_lisp (lres->ai_addr,
-						  lres->ai_addrlen),
-			   addresses);
+        {
+#ifndef AF_INET6
+          if (lres->ai_family != AF_INET)
+            continue;
+#endif
+          addresses = Fcons (conv_sockaddr_to_lisp (lres->ai_addr,
+                                                    lres->ai_addrlen),
+                             addresses);
+        }
       addresses = Fnreverse (addresses);
 
       freeaddrinfo (res);
diff --git a/test/src/process-tests.el b/test/src/process-tests.el
index 158c036aaa7..f065d393d2a 100644
--- a/test/src/process-tests.el
+++ b/test/src/process-tests.el
@@ -337,7 +337,8 @@ See Bug#30460."
   (skip-unless (not (getenv "EMACS_HYDRA_CI")))
   (should-error (network-lookup-address-info "google.com" 'both))
   (should (network-lookup-address-info "google.com" 'ipv4))
-  (should (network-lookup-address-info "google.com" 'ipv6)))
+  (when (featurep 'make-network-process '(:family ipv6))
+    (should (network-lookup-address-info "google.com" 'ipv6))))
 
 (ert-deftest lookup-unicode-domains ()
   "Unicode domains should fail"
@@ -354,11 +355,11 @@ See Bug#30460."
   "Check that we can look up google IP addresses"
   (skip-unless (not (getenv "EMACS_HYDRA_CI")))
   (let ((addresses-both (network-lookup-address-info "google.com"))
-        (addresses-v4 (network-lookup-address-info "google.com" 'ipv4))
-        (addresses-v6 (network-lookup-address-info "google.com" 'ipv6)))
+        (addresses-v4 (network-lookup-address-info "google.com" 'ipv4)))
     (should addresses-both)
-    (should addresses-v4)
-    (should addresses-v6)))
+    (should addresses-v4))
+  (when (featurep 'make-network-process '(:family ipv6))
+    (should (network-lookup-address-info "google.com" 'ipv6))))
 
 (ert-deftest non-existent-lookup-failure ()
   (skip-unless (not (getenv "EMACS_HYDRA_CI")))
-- 
2.39.5