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f7a9f78 Jan 4, 2016
389 lines (319 sloc) 8.4 KB
/* Determine protocol families for which interfaces exist. Linux version.
Copyright (C) 2003-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C 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.
The GNU C 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.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <ifaddrs.h>
#include <netdb.h>
#include <stddef.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <stdint.h>
#include <sys/socket.h>
#include <asm/types.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <not-cancel.h>
#include <libc-lock.h>
#include <atomic.h>
#include <nscd/nscd-client.h>
#include "netlinkaccess.h"
#ifndef IFA_F_HOMEADDRESS
# define IFA_F_HOMEADDRESS 0
#endif
#ifndef IFA_F_OPTIMISTIC
# define IFA_F_OPTIMISTIC 0
#endif
struct cached_data
{
uint32_t timestamp;
uint32_t usecnt;
bool seen_ipv4;
bool seen_ipv6;
size_t in6ailen;
struct in6addrinfo in6ai[0];
};
static struct cached_data noai6ai_cached =
{
.usecnt = 1, /* Make sure we never try to delete this entry. */
.in6ailen = 0
};
static struct cached_data *cache;
__libc_lock_define_initialized (static, lock);
#if IS_IN (nscd)
static uint32_t nl_timestamp;
uint32_t
__bump_nl_timestamp (void)
{
if (atomic_increment_val (&nl_timestamp) == 0)
atomic_increment (&nl_timestamp);
return nl_timestamp;
}
#endif
static inline uint32_t
get_nl_timestamp (void)
{
#if IS_IN (nscd)
return nl_timestamp;
#elif defined USE_NSCD
return __nscd_get_nl_timestamp ();
#else
return 0;
#endif
}
static inline bool
cache_valid_p (void)
{
if (cache != NULL)
{
uint32_t timestamp = get_nl_timestamp ();
return timestamp != 0 && cache->timestamp == timestamp;
}
return false;
}
static struct cached_data *
make_request (int fd, pid_t pid)
{
struct cached_data *result = NULL;
size_t result_len = 0;
size_t result_cap = 32;
struct req
{
struct nlmsghdr nlh;
struct rtgenmsg g;
/* struct rtgenmsg consists of a single byte. This means there
are three bytes of padding included in the REQ definition.
We make them explicit here. */
char pad[3];
} req;
struct sockaddr_nl nladdr;
req.nlh.nlmsg_len = sizeof (req);
req.nlh.nlmsg_type = RTM_GETADDR;
req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
req.nlh.nlmsg_pid = 0;
req.nlh.nlmsg_seq = time (NULL);
req.g.rtgen_family = AF_UNSPEC;
assert (sizeof (req) - offsetof (struct req, pad) == 3);
memset (req.pad, '\0', sizeof (req.pad));
memset (&nladdr, '\0', sizeof (nladdr));
nladdr.nl_family = AF_NETLINK;
#ifdef PAGE_SIZE
const size_t buf_size = PAGE_SIZE;
#else
const size_t buf_size = 4096;
#endif
char buf[buf_size];
struct iovec iov = { buf, buf_size };
if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
(struct sockaddr *) &nladdr,
sizeof (nladdr))) < 0)
goto out_fail;
bool done = false;
bool seen_ipv4 = false;
bool seen_ipv6 = false;
do
{
struct msghdr msg =
{
(void *) &nladdr, sizeof (nladdr),
&iov, 1,
NULL, 0,
0
};
ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
__netlink_assert_response (fd, read_len);
if (read_len < 0)
goto out_fail;
if (msg.msg_flags & MSG_TRUNC)
goto out_fail;
struct nlmsghdr *nlmh;
for (nlmh = (struct nlmsghdr *) buf;
NLMSG_OK (nlmh, (size_t) read_len);
nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
{
if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
|| nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
continue;
if (nlmh->nlmsg_type == RTM_NEWADDR)
{
struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
struct rtattr *rta = IFA_RTA (ifam);
size_t len = nlmh->nlmsg_len - NLMSG_LENGTH (sizeof (*ifam));
if (ifam->ifa_family != AF_INET
&& ifam->ifa_family != AF_INET6)
continue;
const void *local = NULL;
const void *address = NULL;
while (RTA_OK (rta, len))
{
switch (rta->rta_type)
{
case IFA_LOCAL:
local = RTA_DATA (rta);
break;
case IFA_ADDRESS:
address = RTA_DATA (rta);
goto out;
}
rta = RTA_NEXT (rta, len);
}
if (local != NULL)
{
address = local;
out:
if (ifam->ifa_family == AF_INET)
{
if (*(const in_addr_t *) address
!= htonl (INADDR_LOOPBACK))
seen_ipv4 = true;
}
else
{
if (!IN6_IS_ADDR_LOOPBACK (address))
seen_ipv6 = true;
}
}
if (result_len == 0 || result_len == result_cap)
{
result_cap = 2 * result_cap;
result = realloc (result, sizeof (*result)
+ result_cap
* sizeof (struct in6addrinfo));
}
if (!result)
goto out_fail;
struct in6addrinfo *info = &result->in6ai[result_len++];
info->flags = (((ifam->ifa_flags
& (IFA_F_DEPRECATED | IFA_F_OPTIMISTIC))
? in6ai_deprecated : 0)
| ((ifam->ifa_flags & IFA_F_HOMEADDRESS)
? in6ai_homeaddress : 0));
info->prefixlen = ifam->ifa_prefixlen;
info->index = ifam->ifa_index;
if (ifam->ifa_family == AF_INET)
{
info->addr[0] = 0;
info->addr[1] = 0;
info->addr[2] = htonl (0xffff);
info->addr[3] = *(const in_addr_t *) address;
}
else
memcpy (info->addr, address, sizeof (info->addr));
}
else if (nlmh->nlmsg_type == NLMSG_DONE)
/* We found the end, leave the loop. */
done = true;
}
}
while (! done);
if (seen_ipv6 && result != NULL)
{
result->timestamp = get_nl_timestamp ();
result->usecnt = 2;
result->seen_ipv4 = seen_ipv4;
result->seen_ipv6 = true;
result->in6ailen = result_len;
}
else
{
free (result);
atomic_add (&noai6ai_cached.usecnt, 2);
noai6ai_cached.seen_ipv4 = seen_ipv4;
noai6ai_cached.seen_ipv6 = seen_ipv6;
result = &noai6ai_cached;
}
return result;
out_fail:
free (result);
return NULL;
}
void
attribute_hidden
__check_pf (bool *seen_ipv4, bool *seen_ipv6,
struct in6addrinfo **in6ai, size_t *in6ailen)
{
*in6ai = NULL;
*in6ailen = 0;
struct cached_data *olddata = NULL;
struct cached_data *data = NULL;
__libc_lock_lock (lock);
if (cache_valid_p ())
{
data = cache;
atomic_increment (&cache->usecnt);
}
else
{
int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if (__glibc_likely (fd >= 0))
{
struct sockaddr_nl nladdr;
memset (&nladdr, '\0', sizeof (nladdr));
nladdr.nl_family = AF_NETLINK;
socklen_t addr_len = sizeof (nladdr);
if (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
&& __getsockname (fd, (struct sockaddr *) &nladdr,
&addr_len) == 0)
data = make_request (fd, nladdr.nl_pid);
close_not_cancel_no_status (fd);
}
if (data != NULL)
{
olddata = cache;
cache = data;
}
}
__libc_lock_unlock (lock);
if (data != NULL)
{
/* It worked. */
*seen_ipv4 = data->seen_ipv4;
*seen_ipv6 = data->seen_ipv6;
*in6ailen = data->in6ailen;
*in6ai = data->in6ai;
if (olddata != NULL && olddata->usecnt > 0
&& atomic_add_zero (&olddata->usecnt, -1))
free (olddata);
return;
}
/* We cannot determine what interfaces are available. Be
pessimistic. */
*seen_ipv4 = true;
*seen_ipv6 = true;
}
/* Free the cache if it has been allocated. */
libc_freeres_fn (freecache)
{
if (cache)
__free_in6ai (cache->in6ai);
}
void
__free_in6ai (struct in6addrinfo *ai)
{
if (ai != NULL)
{
struct cached_data *data =
(struct cached_data *) ((char *) ai
- offsetof (struct cached_data, in6ai));
if (atomic_add_zero (&data->usecnt, -1))
{
__libc_lock_lock (lock);
if (data->usecnt == 0)
/* Still unused. */
free (data);
__libc_lock_unlock (lock);
}
}
}