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ipv6: cache the result of the DNS query only, the socket needs to be re-created every time

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This commit is contained in:
Michael Stapelberg 2010-01-04 11:16:59 +01:00
parent 37882cee88
commit ced822f461
1 changed files with 43 additions and 30 deletions
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73
src/print_ipv6_addr.c
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@ -1,5 +1,6 @@
// vim:ts=8:expandtab
#include <stdio.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
@ -8,17 +9,38 @@
#include <string.h>
#include <arpa/inet.h>
static void print_sockname(int fd) {
static bool print_sockname(struct addrinfo *addr) {
static char buf[INET6_ADDRSTRLEN+1];
struct sockaddr_storage local;
int ret;
int fd;
if ((fd = socket(addr->ai_family, SOCK_DGRAM, 0)) == -1) {
perror("socket()");
return false;
}
/* 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, addr->ai_addr, addr->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);
return false;
}
socklen_t local_len = sizeof(struct sockaddr_storage);
if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) {
perror("getsockname()");
(void)close(fd);
printf("no IPv6");
return;
return true;
}
memset(buf, 0, INET6_ADDRSTRLEN + 1);
@ -26,11 +48,14 @@ static void print_sockname(int fd) {
buf, sizeof(buf), NULL, 0,
NI_NUMERICHOST)) != 0) {
fprintf(stderr, "getnameinfo(): %s\n", gai_strerror(ret));
(void)close(fd);
printf("no IPv6");
return;
return true;
}
(void)close(fd);
printf("%s", buf);
return true;
}
/*
@ -40,14 +65,13 @@ static void print_sockname(int fd) {
static void print_ipv6_addr() {
struct addrinfo hints;
struct addrinfo *result, *resp;
static int fd = -1;
static struct addrinfo *cached = NULL;
/* To save dns lookups (if they are not cached locally) and creating
* sockets, we save the fd and keep it open. */
if (fd > -1) {
print_sockname(fd);
return;
}
if (cached != NULL)
if (print_sockname(cached))
return;
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = AF_INET6;
@ -64,33 +88,22 @@ static void print_ipv6_addr() {
}
for (resp = result; resp != NULL; resp = resp->ai_next) {
if ((fd = socket(resp->ai_family, SOCK_DGRAM, 0)) == -1) {
perror("socket()");
if (!print_sockname(resp))
continue;
if ((cached = malloc(sizeof(struct addrinfo))) == NULL)
return;
memcpy(cached, resp, sizeof(struct addrinfo));
if ((cached->ai_addr = malloc(resp->ai_addrlen)) == NULL) {
cached = NULL;
return;
}
/* 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;
}
free(result);
print_sockname(fd);
memcpy(cached->ai_addr, resp->ai_addr, resp->ai_addrlen);
freeaddrinfo(result);
return;
}
free(result);
freeaddrinfo(result);
printf("no IPv6");
}