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@xperia64

xperia64/bind.c

Last active Oct 16, 2018
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IPv6 bind shim
/*
Copyright (C) 2000 Daniel Ryde
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
*/
/*
LD_PRELOAD library to make bind and connect to use a virtual
IP address as localaddress. Specified via the enviroment
variable BIND_ADDR.
Compile on Linux with:
gcc -nostartfiles -fpic -shared bind.c -o bind.so -ldl -D_GNU_SOURCE
Example in bash to make inetd only listen to the localhost
lo interface, thus disabling remote connections and only
enable to/from localhost:
BIND_ADDR="127.0.0.1" LD_PRELOAD=./bind.so /sbin/inetd
Example in bash to use your virtual IP as your outgoing
sourceaddress for ircII:
BIND_ADDR="your-virt-ip" LD_PRELOAD=./bind.so ircII
Note that you have to set up your servers virtual IP first.
This program was made by Daniel Ryde
email: daniel@ryde.net
web: http://www.ryde.net/
TODO: I would like to extend it to the accept calls too, like a
general tcp-wrapper. Also like an junkbuster for web-banners.
For libc5 you need to replace socklen_t with int.
*/
/*
This is an updated version of Daniel Ryde's bind.c shim for IPv6
To override an IPv6 bind address, LD_PRELOAD the library as usual
but also set BIND_ADDR6
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <dlfcn.h>
#include <errno.h>
#include <string.h>
int (*real_bind)(int, const struct sockaddr *, socklen_t);
int (*real_connect)(int, const struct sockaddr *, socklen_t);
char *bind_addr_env;
char *bind_addr6_env;
unsigned long int bind_addr_saddr;
unsigned char bind_addr_saddr6[16];
unsigned long int inaddr_any_saddr;
struct sockaddr_in local_sockaddr_in[] = { 0 };
struct sockaddr_in6 local_sockaddr_in6[] = { 0 };
void _init (void)
{
const char *err;
real_bind = dlsym (RTLD_NEXT, "bind");
if ((err = dlerror ()) != NULL) {
fprintf (stderr, "dlsym (bind): %s\n", err);
}
real_connect = dlsym (RTLD_NEXT, "connect");
if ((err = dlerror ()) != NULL) {
fprintf (stderr, "dlsym (connect): %s\n", err);
}
inaddr_any_saddr = htonl (INADDR_ANY);
if (bind_addr_env = getenv ("BIND_ADDR")) {
bind_addr_saddr = inet_addr (bind_addr_env);
local_sockaddr_in->sin_family = AF_INET;
local_sockaddr_in->sin_addr.s_addr = bind_addr_saddr;
local_sockaddr_in->sin_port = htons (0);
}
if (bind_addr6_env = getenv ("BIND_ADDR6")) {
if (inet_pton(AF_INET6, bind_addr6_env, bind_addr_saddr6) > 0) {
local_sockaddr_in6->sin6_family = AF_INET6;
memcpy(local_sockaddr_in6->sin6_addr.s6_addr, bind_addr_saddr6, 16);
local_sockaddr_in6->sin6_port = htons (0);
}
}
}
int bind (int fd, const struct sockaddr *sk, socklen_t sl)
{
/* printf("bind: %d %s:%d\n", fd, inet_ntoa (lsk_in->sin_addr.s_addr),
ntohs (lsk_in->sin_port));*/
if ((sk->sa_family == AF_INET) && (bind_addr_env)) {
static struct sockaddr_in *lsk_in;
lsk_in = (struct sockaddr_in *)sk;
lsk_in->sin_addr.s_addr = bind_addr_saddr;
} else if ((sk->sa_family == AF_INET6) && (bind_addr6_env)) {
static struct sockaddr_in6 *lsk_in6;
lsk_in6 = (struct sockaddr_in6 *)sk;
memcpy(lsk_in6->sin6_addr.s6_addr, bind_addr_saddr6, 16);
}
return real_bind (fd, sk, sl);
}
int connect (int fd, const struct sockaddr *sk, socklen_t sl)
{
/* printf("connect: %d %s:%d\n", fd, inet_ntoa (rsk_in->sin_addr.s_addr),
ntohs (rsk_in->sin_port));*/
if ((sk->sa_family == AF_INET) && (bind_addr_env)) {
static struct sockaddr_in *rsk_in;
rsk_in = (struct sockaddr_in *)sk;
real_bind (fd, (struct sockaddr *)local_sockaddr_in, sizeof (struct sockaddr));
} else if ((sk->sa_family == AF_INET6) && (bind_addr6_env)) {
static struct sockaddr_in6 *rsk_in6;
rsk_in6 = (struct sockaddr_in6 *)sk;
real_bind (fd, (struct sockaddr *)local_sockaddr_in6, sizeof (struct sockaddr_in6));
}
return real_connect (fd, sk, sl);
}
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