diff options
Diffstat (limited to 'src/get_ipv6_addr.c')
| -rw-r--r-- | src/get_ipv6_addr.c | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/src/get_ipv6_addr.c b/src/get_ipv6_addr.c index 95a06a6..2fd978b 100644 --- a/src/get_ipv6_addr.c +++ b/src/get_ipv6_addr.c @@ -21,19 +21,28 @@ const char *get_ipv6_addr() { 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) { perror("getaddrinfo()"); return "no IP"; } for (resp = result; resp != NULL; resp = resp->ai_next) { - if ((fd = socket(resp->ai_family, SOCK_STREAM, 0)) == -1) { + 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) { perror("connect()"); + (void)close(fd); continue; } @@ -41,18 +50,21 @@ const char *get_ipv6_addr() { socklen_t local_len = sizeof(struct sockaddr_storage); if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) { perror("getsockname()"); + (void)close(fd); return "no IP"; } + (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) { + 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; } |