Add dual stack support

We now can pass NULL instead of an IPV4/IPV6 address to use both
chouquette · Aug 26, 2020 · 1b4b07e · 1b4b07e
1 parent c30f2b0
commit 1b4b07e
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Showing 4 changed files with 34 additions and 6 deletions.
diff --git a/examples/announce.c b/examples/announce.c
@@ -127,7 +127,7 @@ int main(int argc, char *argv[])
         signal(SIGINT, sighandler);
         signal(SIGTERM, sighandler);
 
-        if ((r = mdns_init(&ctx, MDNS_ADDR_IPV4, MDNS_PORT)) < 0)
+        if ((r = mdns_init(&ctx, NULL, MDNS_PORT)) < 0)
                 goto err;
 
         // test with `ping mdnshost.local` after discovery (run ./test first)

diff --git a/examples/main.c b/examples/main.c
@@ -77,7 +77,7 @@ int main(int i_argc, char *ppsz_argv[])
         }
         signal(SIGINT, &sighandler);
 
-        if ((r = mdns_init(&ctx, MDNS_ADDR_IPV4, MDNS_PORT)) < 0)
+        if ((r = mdns_init(&ctx, NULL, MDNS_PORT)) < 0)
                 goto err;
         if ((r = mdns_listen(ctx, ppsz_names, i_nb_names, RR_PTR, 10, stop,
                              callback, NULL)) < 0)

diff --git a/include/microdns/microdns.h b/include/microdns/microdns.h
@@ -90,7 +90,7 @@ typedef bool (*mdns_stop_func)(void*);
  * @brief Allocates and initialize a new mdns context
  *
  * @param ctx Returns the allocated context for the library [OUT]
- * @param addr Address to listen to
+ * @param addr Protocol specific address to listen to, or NULL to use both IPv4 and IPv6
  * @param port Port to listen on
  *
  * @see use mdns_destroy() to clean

diff --git a/src/mdns.c b/src/mdns.c
@@ -359,12 +359,40 @@ mdns_resolve(struct mdns_ctx *ctx, const char *addr, unsigned short port)
 
         sprintf(buf, "%hu", port);
         memset(&hints, 0, sizeof(hints));
-        hints.ai_family = AF_UNSPEC;
         hints.ai_socktype = SOCK_DGRAM;
         hints.ai_flags = AI_NUMERICHOST | AI_NUMERICSERV;
-        errno = getaddrinfo(addr, buf, &hints, &res);
-        if (errno != 0)
+
+        if (addr == NULL) {
+            hints.ai_family = AF_INET;
+            /* First, get the ipv4 multicast address info */
+            errno = getaddrinfo(MDNS_ADDR_IPV4, buf, &hints, &res);
+            if (errno != 0)
+                    return (MDNS_LKPERR);
+            /* Now get the ipv6 informations and link them with the ipv4 ones */
+            struct addrinfo *ipv6_res = NULL;
+            hints.ai_family = AF_INET6;
+            errno = getaddrinfo(MDNS_ADDR_IPV6, buf, &hints, &ipv6_res);
+            if (errno != 0) {
+                    freeaddrinfo(res);
+                    return (MDNS_LKPERR);
+            }
+            struct addrinfo* ipv4 = res;
+            for (; ipv4->ai_next != NULL; ipv4 = ipv4->ai_next)
+                ;
+            ipv4->ai_next = ipv6_res;
+        } else {
+            int family;
+            if (!strcmp(addr, MDNS_ADDR_IPV4))
+                family = AF_INET;
+            else if (!strcmp(addr, MDNS_ADDR_IPV6))
+                family = AF_INET6;
+            else
                 return (MDNS_LKPERR);
+            hints.ai_family = family;
+            errno = getaddrinfo(addr, buf, &hints, &res);
+            if (errno != 0)
+                    return (MDNS_LKPERR);
+        }
 
         status = mdns_list_interfaces(&ifaddrs, &mdns_ips, &ctx->nb_conns, &mcast_addrs, res);
         if ( status < 0) {