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get_ipv6_addr: more documentation, use SOCK_DGRAM, reformat

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This commit is contained in:
Michael Stapelberg 2009-07-21 20:35:19 +02:00
parent 230f3167b7
commit a1eda7b209
1 changed files with 20 additions and 8 deletions
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28
src/get_ipv6_addr.c
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@ -21,19 +21,28 @@ const char *get_ipv6_addr() {
memset(&hints, 0, sizeof(struct addrinfo)); memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = AF_INET6; 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) { if (getaddrinfo("k.root-servers.net", "domain", &hints, &result) != 0) {
perror("getaddrinfo()"); perror("getaddrinfo()");
return "no IP"; return "no IP";
} }
for (resp = result; resp != NULL; resp = resp->ai_next) { 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()"); perror("socket()");
continue; 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) { if (connect(fd, resp->ai_addr, resp->ai_addrlen) == -1) {
perror("connect()"); perror("connect()");
(void)close(fd);
continue; continue;
} }
@ -41,18 +50,21 @@ const char *get_ipv6_addr() {
socklen_t local_len = sizeof(struct sockaddr_storage); socklen_t local_len = sizeof(struct sockaddr_storage);
if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) { if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) {
perror("getsockname()"); perror("getsockname()");
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) {
fprintf(stderr, "getnameinfo(): %s\n", gai_strerror(ret));
return "no IP"; return "no IP";
} }
(void)close(fd); (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 IP";
}
free(result); free(result);
return buf; return buf;
} }