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/* $Id: getroute.c,v 1.6 2015/04/26 14:43:28 nanard Exp $ */
/* MiniUPnP project
* http://miniupnp.free.fr/ or http://miniupnp.tuxfamily.org/
* (c) 2006-2015 Thomas Bernard
* This software is subject to the conditions detailed
* in the LICENCE file provided within the distribution */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
/*#include <linux/in_route.h>*/
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#ifdef USE_LIBNFNETLINK
/* define USE_LIBNFNETLINK in order to use libnfnetlink
* instead of custom code
* see https://github.com/miniupnp/miniupnp/issues/110 */
#include <libnfnetlink/libnfnetlink.h>
#endif /* USE_LIBNFNETLINK */
#include "../getroute.h"
#include "../upnputils.h"
int
get_src_for_route_to(const struct sockaddr * dst,
void * src, size_t * src_len,
int * index)
{
int fd = -1;
struct nlmsghdr *h;
int status;
struct {
struct nlmsghdr n;
struct rtmsg r;
char buf[1024];
} req;
struct sockaddr_nl nladdr;
struct iovec iov = {
.iov_base = (void*) &req.n,
};
struct msghdr msg = {
.msg_name = &nladdr,
.msg_namelen = sizeof(nladdr),
.msg_iov = &iov,
.msg_iovlen = 1,
};
const struct sockaddr_in * dst4;
const struct sockaddr_in6 * dst6;
#ifndef USE_LIBNFNETLINK
struct rtattr * rta;
#endif /* USE_LIBNFNETLINK */
memset(&req, 0, sizeof(req));
req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
req.n.nlmsg_flags = NLM_F_REQUEST;
req.n.nlmsg_type = RTM_GETROUTE;
req.r.rtm_family = dst->sa_family;
req.r.rtm_table = 0;
req.r.rtm_protocol = 0;
req.r.rtm_scope = 0;
req.r.rtm_type = 0;
req.r.rtm_src_len = 0;
req.r.rtm_dst_len = 0;
req.r.rtm_tos = 0;
{
char dst_str[128];
sockaddr_to_string(dst, dst_str, sizeof(dst_str));
syslog(LOG_DEBUG, "get_src_for_route_to (%s)", dst_str);
}
/* add address */
#ifndef USE_LIBNFNETLINK
rta = (struct rtattr *)(((char*)&req) + NLMSG_ALIGN(req.n.nlmsg_len));
rta->rta_type = RTA_DST;
#endif /* USE_LIBNFNETLINK */
if(dst->sa_family == AF_INET) {
dst4 = (const struct sockaddr_in *)dst;
#ifdef USE_LIBNFNETLINK
nfnl_addattr_l(&req.n, sizeof(req), RTA_DST, &dst4->sin_addr, 4);
#else
rta->rta_len = RTA_SPACE(sizeof(dst4->sin_addr));
memcpy(RTA_DATA(rta), &dst4->sin_addr, sizeof(dst4->sin_addr));
#endif /* USE_LIBNFNETLINK */
req.r.rtm_dst_len = 32;
} else {
dst6 = (const struct sockaddr_in6 *)dst;
#ifdef USE_LIBNFNETLINK
nfnl_addattr_l(&req.n, sizeof(req), RTA_DST, &dst6->sin6_addr, 16);
#else
rta->rta_len = RTA_SPACE(sizeof(dst6->sin6_addr));
memcpy(RTA_DATA(rta), &dst6->sin6_addr, sizeof(dst6->sin6_addr));
#endif /* USE_LIBNFNETLINK */
req.r.rtm_dst_len = 128;
}
#ifndef USE_LIBNFNETLINK
req.n.nlmsg_len += rta->rta_len;
#endif /* USE_LIBNFNETLINK */
fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if (fd < 0) {
syslog(LOG_ERR, "socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE) : %m");
return -1;
}
memset(&nladdr, 0, sizeof(nladdr));
nladdr.nl_family = AF_NETLINK;
req.n.nlmsg_seq = 1;
iov.iov_len = req.n.nlmsg_len;
status = sendmsg(fd, &msg, 0);
if (status < 0) {
syslog(LOG_ERR, "sendmsg(rtnetlink) : %m");
goto error;
}
memset(&req, 0, sizeof(req));
for(;;) {
iov.iov_len = sizeof(req);
status = recvmsg(fd, &msg, 0);
if(status < 0) {
if (errno == EINTR || errno == EAGAIN)
continue;
syslog(LOG_ERR, "recvmsg(rtnetlink) %m");
goto error;
}
if(status == 0) {
syslog(LOG_ERR, "recvmsg(rtnetlink) EOF");
goto error;
}
for (h = (struct nlmsghdr*)&req.n; status >= (int)sizeof(*h); ) {
int len = h->nlmsg_len;
int l = len - sizeof(*h);
if (l<0 || len>status) {
if (msg.msg_flags & MSG_TRUNC) {
syslog(LOG_ERR, "Truncated message");
}
syslog(LOG_ERR, "malformed message: len=%d", len);
goto error;
}
if(nladdr.nl_pid != 0 || h->nlmsg_seq != 1/*seq*/) {
syslog(LOG_ERR, "wrong seq = %d\n", h->nlmsg_seq);
/* Don't forget to skip that message. */
status -= NLMSG_ALIGN(len);
h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len));
continue;
}
if(h->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h);
syslog(LOG_ERR, "NLMSG_ERROR %d : %s", err->error, strerror(-err->error));
goto error;
}
if(h->nlmsg_type == RTM_NEWROUTE) {
struct rtattr * rta;
int len = h->nlmsg_len;
len -= NLMSG_LENGTH(sizeof(struct rtmsg));
for(rta = RTM_RTA(NLMSG_DATA((h))); RTA_OK(rta, len); rta = RTA_NEXT(rta,len)) {
unsigned char * data = RTA_DATA(rta);
if(rta->rta_type == RTA_PREFSRC) {
if(src_len && src) {
if(*src_len < RTA_PAYLOAD(rta)) {
syslog(LOG_WARNING, "cannot copy src: %u<%lu",
(unsigned)*src_len, (unsigned long)RTA_PAYLOAD(rta));
goto error;
}
*src_len = RTA_PAYLOAD(rta);
memcpy(src, data, RTA_PAYLOAD(rta));
}
} else if(rta->rta_type == RTA_OIF) {
if(index)
memcpy(index, data, sizeof(int));
}
}
close(fd);
return 0;
}
status -= NLMSG_ALIGN(len);
h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len));
}
}
syslog(LOG_WARNING, "get_src_for_route_to() : src not found");
error:
if(fd >= 0)
close(fd);
return -1;
}
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