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#define _GNU_SOURCE
#include <sys/socket.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdlib.h>
#include <netinet/in.h>
int
connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
{
unsigned short port;
static int (*next_connect)(int, const struct sockaddr *, socklen_t);
if (next_connect == NULL) {
next_connect = dlsym(RTLD_NEXT, "connect");
if (next_connect == NULL) {
errno = ENOSYS;
return -1;
}
}
if (getenv("NOPORT53") == NULL) {
return next_connect(sockfd, addr, addrlen);
}
switch (addr->sa_family) {
case AF_INET:
port = ntohs(((struct sockaddr_in *)addr)->sin_port);
if (port == 53) {
errno = ECONNREFUSED;
return -1;
}
break;
case AF_INET6:
port = ntohs(((struct sockaddr_in6 *)addr)->sin6_port);
if (port == 53) {
errno = ECONNREFUSED;
return -1;
}
break;
default:
break;
}
return next_connect(sockfd, addr, addrlen);
}
ssize_t
sendto(int sockfd, const void *buf, size_t len, int flags,
const struct sockaddr *dest_addr, socklen_t addrlen)
{
unsigned short port;
static int (*next_sendto)(int, const void *, size_t, int,
const struct sockaddr *, socklen_t);
if (next_sendto == NULL) {
next_sendto = dlsym(RTLD_NEXT, "sendto");
if (next_sendto == NULL) {
errno = ENOSYS;
return -1;
}
}
if (getenv("NOPORT53") == NULL) {
return next_sendto(sockfd, buf, len, flags, dest_addr, addrlen);
}
switch (dest_addr->sa_family) {
case AF_INET:
port = ntohs(((struct sockaddr_in *)dest_addr)->sin_port);
if (port == 53) {
errno = ECONNREFUSED;
return -1;
}
break;
case AF_INET6:
port = ntohs(((struct sockaddr_in6 *)dest_addr)->sin6_port);
if (port == 53) {
errno = ECONNREFUSED;
return -1;
}
break;
default:
break;
}
return next_sendto(sockfd, buf, len, flags, dest_addr, addrlen);
}
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