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/*
* Copyright © 2010,2012 Joachim Breitner
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* This file incorporates some code from the nss-mdns module,
* © 2004 Lennart Poettering.
*/
#include <netlink/socket.h>
#include <netlink/route/route.h>
#include <nss.h>
#include <netdb.h>
#include <errno.h>
#include <sys/socket.h>
typedef struct {
uint32_t address;
} ipv4_address_t;
#define ALIGN(idx) do { \
if (idx % sizeof(void*)) \
idx += (sizeof(void*) - idx % sizeof(void*)); /* Align on 32 bit boundary */ \
} while(0)
static struct nl_addr *
find_gateway() {
struct nl_cache* route_cache;
struct nl_sock *sock;
struct nl_object *obj;
struct nl_addr *gw = NULL;
int err;
// Allocate a new netlink socket
sock = nl_socket_alloc();
err = nl_connect(sock, NETLINK_ROUTE);
if (err) {
nl_socket_free(sock);
return NULL;
}
if (rtnl_route_alloc_cache(sock, AF_INET, 0, &route_cache)) {
nl_close(sock);
nl_socket_free(sock);
return NULL;
}
for (obj = nl_cache_get_first(route_cache); obj; obj = nl_cache_get_next(obj)) {
struct rtnl_route *route = (struct rtnl_route *)obj;
// Ignore non ipv4 routes
if (rtnl_route_get_family(route) != AF_INET) continue;
// Find a default route
if (nl_addr_get_prefixlen(rtnl_route_get_dst(route)) != 0) continue;
// Assert a next hop
if (rtnl_route_get_nnexthops(route) < 1) continue;
// Found a gateway
struct nl_addr *gw_ = rtnl_route_nh_get_gateway(rtnl_route_nexthop_n(route, 0));
if (!gw_) continue;
// Consider only the main route table
if (rtnl_route_get_table(route) != RT_TABLE_MAIN) continue;
// Clone the address, as this one will be freed with the route cache (will it?)
gw = nl_addr_clone(gw_);
if (!gw) continue;
break;
//char buf[100];
//printf("Addr: %s\n", nl_addr2str(dst,buf,100));
}
// Free the cache
nl_cache_free(route_cache);
// Close the socket first to release kernel memory
nl_close(sock);
// Finally destroy the netlink handle
nl_socket_free(sock);
return gw;
}
enum nss_status _nss_gw_name_gethostbyname_r (
const char *name,
struct hostent *result,
char *buffer,
size_t buflen,
int *errnop,
int *h_errnop) {
size_t idx, astart;
struct nl_addr *gw;
if (!strcmp(name,"gateway.localhost")) {
// Look up gatway
gw = find_gateway();
if (!gw) {
*errnop = EAGAIN;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_TRYAGAIN;
}
if (buflen <
sizeof(char*)+ /* alias names */
strlen(name)+1+ /* main name */
sizeof(ipv4_address_t)+ /* address */
sizeof(char*)+ /* null address pointer */
8 /* Alignment */
) { /* official name */
nl_addr_put(gw);
*errnop = ERANGE;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_TRYAGAIN;
}
/* Alias names */
*((char**) buffer) = NULL;
result->h_aliases = (char**) buffer;
idx = sizeof(char*);
/* Official name */
strcpy(buffer+idx, name);
result->h_name = buffer+idx;
idx += strlen(name)+1;
ALIGN(idx);
result->h_addrtype = AF_INET;
result->h_length = sizeof(ipv4_address_t);
astart = idx;
memcpy(buffer+astart, nl_addr_get_binary_addr(gw), sizeof(ipv4_address_t));
idx += sizeof(ipv4_address_t);
result->h_addr_list = (char**)(buffer + idx);
result->h_addr_list[0] = buffer + astart;
result->h_addr_list[1] = NULL;
nl_addr_put(gw);
return NSS_STATUS_SUCCESS;
}{
*errnop = EINVAL;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
}
}
enum nss_status _nss_gw_name_gethostbyname2_r(
const char *name,
int af,
struct hostent * result,
char *buffer,
size_t buflen,
int *errnop,
int *h_errnop) {
if (af != AF_INET) {
*errnop = EAGAIN;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_TRYAGAIN;
} else {
return _nss_gw_name_gethostbyname_r(name, result, buffer, buflen, errnop, h_errnop);
}
}
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