From 3fa9e5724821cd93aa37659f7be8edb475f1f155 Mon Sep 17 00:00:00 2001
From: Max Lv <max.c.lv@gmail.com>
Date: Sun, 10 Mar 2019 07:40:07 +0800
Subject: [PATCH] Refine ipv6only handling

---
 src/local.c    |  8 ++++++--
 src/netutils.c | 14 +++++++-------
 src/netutils.h |  2 +-
 src/redir.c    |  8 ++++++--
 src/server.c   |  2 +-
 src/tunnel.c   |  8 ++++++--
 6 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/src/local.c b/src/local.c
index 949053eb..d998fd33 100644
--- a/src/local.c
+++ b/src/local.c
@@ -1708,7 +1708,7 @@ main(int argc, char **argv)
             FATAL("failed to find a free port");
         }
         snprintf(tmp_port, 8, "%d", port);
-        if (is_ipv6only(remote_addr, remote_num)) {
+        if (is_ipv6only(remote_addr, remote_num, ipv6first)) {
             plugin_host = "::1";
         } else {
             plugin_host = "127.0.0.1";
@@ -1748,7 +1748,11 @@ main(int argc, char **argv)
 #endif
 
     if (local_addr == NULL) {
-        local_addr = "127.0.0.1";
+        if (is_ipv6only(remote_addr, remote_num, ipv6first)) {
+            local_addr = "::1";
+        } else {
+            local_addr = "127.0.0.1";
+        }
     }
 
     USE_SYSLOG(argv[0], pid_flags);
diff --git a/src/netutils.c b/src/netutils.c
index 6bc14c72..f18fcd98 100644
--- a/src/netutils.c
+++ b/src/netutils.c
@@ -285,17 +285,17 @@ validate_hostname(const char *hostname, const int hostname_len)
 }
 
 int
-is_ipv6only(ss_addr_t *servers, size_t server_num)
+is_ipv6only(ss_addr_t *servers, size_t server_num, int ipv6first)
 {
-    struct cork_ip ip;
     int i;
     for (i = 0; i < server_num; i++)
     {
-        if (cork_ip_init(&ip, servers[i].host) != -1) {
-            if (ip.version != 6) {
-                return 0;
-            }
-        } else {
+        struct sockaddr_storage storage;
+        memset(&storage, 0, sizeof(struct sockaddr_storage));
+        if (get_sockaddr(servers[i].host, servers[i].port, &storage, 1, ipv6first) == -1) {
+            FATAL("failed to resolve the provided hostname");
+        }
+        if (storage.ss_family != AF_INET6) {
             return 0;
         }
     }
diff --git a/src/netutils.h b/src/netutils.h
index f7f6dc6b..70664f13 100644
--- a/src/netutils.h
+++ b/src/netutils.h
@@ -108,6 +108,6 @@ int sockaddr_cmp_addr(struct sockaddr_storage *addr1,
 
 int validate_hostname(const char *hostname, const int hostname_len);
 
-int is_ipv6only(ss_addr_t *servers, size_t server_num);
+int is_ipv6only(ss_addr_t *servers, size_t server_num, int ipv6first);
 
 #endif
diff --git a/src/redir.c b/src/redir.c
index f5af00bb..a21bf4e3 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -1067,7 +1067,7 @@ main(int argc, char **argv)
             FATAL("failed to find a free port");
         }
         snprintf(tmp_port, 8, "%d", port);
-        if (is_ipv6only(remote_addr, remote_num)) {
+        if (is_ipv6only(remote_addr, remote_num, ipv6first)) {
             plugin_host = "::1";
         } else {
             plugin_host = "127.0.0.1";
@@ -1099,7 +1099,11 @@ main(int argc, char **argv)
 #endif
 
     if (local_addr == NULL) {
-        local_addr = "127.0.0.1";
+        if (is_ipv6only(remote_addr, remote_num, ipv6first)) {
+            local_addr = "::1";
+        } else {
+            local_addr = "127.0.0.1";
+        }
     }
 
     if (fast_open == 1) {
diff --git a/src/server.c b/src/server.c
index c00d5146..1f0467c5 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1835,7 +1835,7 @@ main(int argc, char **argv)
         exit(EXIT_FAILURE);
     }
 
-    if (is_ipv6only(server_addr, server_num)) {
+    if (is_ipv6only(server_addr, server_num, ipv6first)) {
         plugin_host = "::1";
     } else {
         plugin_host = "127.0.0.1";
diff --git a/src/tunnel.c b/src/tunnel.c
index b55b895a..ae9244e6 100644
--- a/src/tunnel.c
+++ b/src/tunnel.c
@@ -1116,7 +1116,7 @@ main(int argc, char **argv)
             FATAL("failed to find a free port");
         }
         snprintf(tmp_port, 8, "%d", port);
-        if (is_ipv6only(remote_addr, remote_num)) {
+        if (is_ipv6only(remote_addr, remote_num, ipv6first)) {
             plugin_host = "::1";
         } else {
             plugin_host = "127.0.0.1";
@@ -1156,7 +1156,11 @@ main(int argc, char **argv)
 #endif
 
     if (local_addr == NULL) {
-        local_addr = "127.0.0.1";
+        if (is_ipv6only(remote_addr, remote_num, ipv6first)) {
+            local_addr = "::1";
+        } else {
+            local_addr = "127.0.0.1";
+        }
     }
 
     if (fast_open == 1) {