From d8bc4631788ebc58c8a505ac1411486cf58fac84 Mon Sep 17 00:00:00 2001
From: Martin Pulec <martin.pulec@cesnet.cz>
Date: Fri, 24 May 2019 22:00:30 +0200
Subject: [PATCH] Default to IPv4 if IPv6 not supported

---
 src/main.cpp    |  5 +++++
 src/utils/net.c | 10 ++++++++++
 src/utils/net.h |  1 +
 3 files changed, 16 insertions(+)

diff --git a/src/main.cpp b/src/main.cpp
index 98fe66322..0f133dfa3 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -939,6 +939,11 @@ int main(int argc, char *argv[])
                 audio_host = requested_receiver;
         }
 
+        if (!is_ipv6_supported()) {
+                log_msg(LOG_LEVEL_WARNING, "IPv6 support missing, setting IPv4-only mode.\n");
+                force_ip_version = 4;
+        }
+
         if (!set_output_buffering()) {
                 log_msg(LOG_LEVEL_WARNING, "Cannot set console output buffering!\n");
         }
diff --git a/src/utils/net.c b/src/utils/net.c
index 3c853e0c6..63888e95e 100644
--- a/src/utils/net.c
+++ b/src/utils/net.c
@@ -297,3 +297,13 @@ bool get_local_addresses(struct sockaddr_storage *addrs, size_t *len, int ip_ver
 #endif
 }
 
+bool is_ipv6_supported(void)
+{
+        int fd = socket(AF_INET6, SOCK_DGRAM, 0);
+        if (fd == INVALID_SOCKET && errno == EAFNOSUPPORT) {
+                return false;
+        }
+        CLOSESOCKET(fd);
+        return true;
+}
+
diff --git a/src/utils/net.h b/src/utils/net.h
index 720b1befa..826e69ffa 100644
--- a/src/utils/net.h
+++ b/src/utils/net.h
@@ -48,6 +48,7 @@ bool is_addr_loopback(struct sockaddr *sa);
 bool is_host_loopback(const char *hostname);
 uint16_t socket_get_recv_port(int fd);
 bool get_local_addresses(struct sockaddr_storage *addrs, size_t *len, int ip_version);
+bool is_ipv6_supported(void);
 
 #ifdef WIN32
 #define CLOSESOCKET closesocket