Add debian changelog entry to keep updates from overwriting local versions

[i3/i3status] / src / get_ipv6_addr.c

diff --git a/src/get_ipv6_addr.c b/src/get_ipv6_addr.c
index 44edc7add472a335700514f2d5a9eb9f7d385adf..341b5ba8ac4fde12a3e9ebb91e02af3ab0545803 100644 (file)
--- a/src/get_ipv6_addr.c
+++ b/src/get_ipv6_addr.c
@@ -1,3 +1,4 @@
+// vim:ts=8:expandtab
 #include <stdio.h>
 #include <unistd.h>
 #include <stdlib.h>
@@ -12,50 +13,67 @@
  *
  */
 const char *get_ipv6_addr() {
-       static char buf[INET6_ADDRSTRLEN+1];
-       struct addrinfo hints;
-       struct addrinfo *result, *resp;
-       int fd;
-
-       memset(&hints, 0, sizeof(struct addrinfo));
-       hints.ai_family = AF_INET6;
-
-       if (getaddrinfo("k.root-servers.net", "domain", &hints, &result) != 0) {
-               perror("getaddrinfo()");
-               return "no IP";
-       }
-
-       for (resp = result; resp != NULL; resp = resp->ai_next) {
-               if ((fd = socket(resp->ai_family, SOCK_STREAM, 0)) == -1) {
-                       perror("socket()");
-                       continue;
-               }
-
-               if (connect(fd, resp->ai_addr, resp->ai_addrlen) == -1) {
-                       perror("connect()");
-                       continue;
-               }
-
-               struct sockaddr_storage local;
-               socklen_t local_len = sizeof(struct sockaddr_storage);
-               if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) {
-                       perror("getsockname()");
-                       return "no IP";
-               }
-
-               memset(buf, 0, INET6_ADDRSTRLEN + 1);
-               int ret;
-               if ((ret = getnameinfo((struct sockaddr*)&local, local_len, buf, sizeof(buf), NULL, 0, NI_NUMERICHOST)) != 0) {
-                       fprintf(stderr, "getnameinfo(): %s\n", gai_strerror(ret));
-                       return "no IP";
-               }
-
-               (void)close(fd);
-
-               free(result);
-               return buf;
-       }
-
-       free(result);
-       return "no IP";
+        static char buf[INET6_ADDRSTRLEN+1];
+        struct addrinfo hints;
+        struct addrinfo *result, *resp;
+        int fd;
+
+        memset(&hints, 0, sizeof(struct addrinfo));
+        hints.ai_family = AF_INET6;
+
+        /* We resolve the K root server to get a public IPv6 address. You can
+         * replace this with any other host which has an AAAA record, but the
+         * K root server is a pretty safe bet. */
+        if (getaddrinfo("k.root-servers.net", "domain", &hints, &result) != 0) {
+                /* We don’t display the error here because most
+                 * likely, there just is no connectivity.
+                 * Thus, don’t spam the user’s console. */
+                return "no IPv6";
+        }
+
+        for (resp = result; resp != NULL; resp = resp->ai_next) {
+                if ((fd = socket(resp->ai_family, SOCK_DGRAM, 0)) == -1) {
+                        perror("socket()");
+                        continue;
+                }
+
+                /* Since the socket was created with SOCK_DGRAM, this is
+                 * actually not establishing a connection or generating
+                 * any other network traffic. Instead, as a side-effect,
+                 * it saves the local address with which packets would
+                 * be sent to the destination. */
+                if (connect(fd, resp->ai_addr, resp->ai_addrlen) == -1) {
+                        /* We don’t display the error here because most
+                         * likely, there just is no IPv6 connectivity.
+                         * Thus, don’t spam the user’s console but just
+                         * try the next address. */
+                        (void)close(fd);
+                        continue;
+                }
+
+                struct sockaddr_storage local;
+                socklen_t local_len = sizeof(struct sockaddr_storage);
+                if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) {
+                        perror("getsockname()");
+                        (void)close(fd);
+                        return "no IPv6";
+                }
+
+                (void)close(fd);
+
+                memset(buf, 0, INET6_ADDRSTRLEN + 1);
+                int ret;
+                if ((ret = getnameinfo((struct sockaddr*)&local, local_len,
+                                       buf, sizeof(buf), NULL, 0,
+                                       NI_NUMERICHOST)) != 0) {
+                        fprintf(stderr, "getnameinfo(): %s\n", gai_strerror(ret));
+                        return "no IPv6";
+                }
+
+                free(result);
+                return buf;
+        }
+
+        free(result);
+        return "no IPv6";
 }