/* dnsmasq is Copyright (c) 2000-2009 Simon Kelley
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; version 2 dated June, 1991, or
(at your option) version 3 dated 29 June, 2007.
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, see <http://www.gnu.org/licenses/>.
*/
#include "dnsmasq.h"
#ifdef HAVE_LINUX_NETWORK
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/types.h>
/* linux 2.6.19 buggers up the headers, patch it up here. */
#ifndef IFA_RTA
#define IFA_RTA(r) ((struct rtattr*) (((char*) (r)) + NLMSG_ALIGN(sizeof(struct ifaddrmsg))))
#include <linux/if_addr.h>
#endif
static struct iovec iov;
static u32 netlink_pid;
static void nl_err(struct nlmsghdr* h);
static void nl_routechange(struct nlmsghdr* h);
void netlink_init(void) {
struct sockaddr_nl addr;
socklen_t slen = sizeof(addr);
addr.nl_family = AF_NETLINK;
addr.nl_pad = 0;
addr.nl_pid = 0; /* autobind */
#ifdef HAVE_IPV6
addr.nl_groups = RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_ROUTE;
#else
addr.nl_groups = RTMGRP_IPV4_ROUTE;
#endif
/* May not be able to have permission to set multicast groups don't die in that case */
if ((daemon->netlinkfd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) != -1) {
if (bind(daemon->netlinkfd, (struct sockaddr*) &addr, sizeof(addr)) == -1) {
addr.nl_groups = 0;
if (errno != EPERM ||
bind(daemon->netlinkfd, (struct sockaddr*) &addr, sizeof(addr)) == -1)
daemon->netlinkfd = -1;
}
}
if (daemon->netlinkfd == -1 ||
getsockname(daemon->netlinkfd, (struct sockaddr*) &addr, &slen) == 1)
die(_("cannot create netlink socket: %s"), NULL, EC_MISC);
/* save pid assigned by bind() and retrieved by getsockname() */
netlink_pid = addr.nl_pid;
iov.iov_len = 100;
iov.iov_base = safe_malloc(iov.iov_len);
}
static ssize_t netlink_recv(void) {
struct msghdr msg;
struct sockaddr_nl nladdr;
ssize_t rc;
while (1) {
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_name = &nladdr;
msg.msg_namelen = sizeof(nladdr);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_flags = 0;
while ((rc = recvmsg(daemon->netlinkfd, &msg, MSG_PEEK | MSG_TRUNC)) == -1 && errno == EINTR)
;
/* make buffer big enough */
if (rc != -1 && (msg.msg_flags & MSG_TRUNC)) {
/* Very new Linux kernels return the actual size needed, older ones always return
* truncated size */
if ((size_t) rc == iov.iov_len) {
if (expand_buf(&iov, rc + 100)) continue;
} else
expand_buf(&iov, rc);
}
/* read it for real */
msg.msg_flags = 0;
while ((rc = recvmsg(daemon->netlinkfd, &msg, 0)) == -1 && errno == EINTR)
;
/* Make sure this is from the kernel */
if (rc == -1 || nladdr.nl_pid == 0) break;
}
/* discard stuff which is truncated at this point (expand_buf() may fail) */
if (msg.msg_flags & MSG_TRUNC) {
rc = -1;
errno = ENOMEM;
}
return rc;
}
int iface_enumerate(void* parm, int (*ipv4_callback)(), int (*ipv6_callback)()) {
struct sockaddr_nl addr;
struct nlmsghdr* h;
ssize_t len;
static unsigned int seq = 0;
int family = AF_INET;
struct {
struct nlmsghdr nlh;
struct rtgenmsg g;
} req;
addr.nl_family = AF_NETLINK;
addr.nl_pad = 0;
addr.nl_groups = 0;
addr.nl_pid = 0; /* address to kernel */
again:
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 | NLM_F_ACK;
req.nlh.nlmsg_pid = 0;
req.nlh.nlmsg_seq = ++seq;
req.g.rtgen_family = family;
/* Don't block in recvfrom if send fails */
while ((len = sendto(daemon->netlinkfd, (void*) &req, sizeof(req), 0, (struct sockaddr*) &addr,
sizeof(addr))) == -1 &&
retry_send())
;
if (len == -1) return 0;
while (1) {
if ((len = netlink_recv()) == -1) {
if (errno == ENOBUFS) {
sleep(1);
goto again;
}
return 0;
}
for (h = (struct nlmsghdr*) iov.iov_base; NLMSG_OK(h, (size_t) len); h = NLMSG_NEXT(h, len))
if (h->nlmsg_seq != seq || h->nlmsg_pid != netlink_pid)
nl_routechange(h); /* May be multicast arriving async */
else if (h->nlmsg_type == NLMSG_ERROR)
nl_err(h);
else if (h->nlmsg_type == NLMSG_DONE) {
#ifdef HAVE_IPV6
if (family == AF_INET && ipv6_callback) {
family = AF_INET6;
goto again;
}
#endif
return 1;
} else if (h->nlmsg_type == RTM_NEWADDR) {
struct ifaddrmsg* ifa = NLMSG_DATA(h);
struct rtattr* rta = IFA_RTA(ifa);
unsigned int len1 = h->nlmsg_len - NLMSG_LENGTH(sizeof(*ifa));
if (ifa->ifa_family == AF_INET) {
struct in_addr netmask, addr, broadcast;
netmask.s_addr = htonl(0xffffffff << (32 - ifa->ifa_prefixlen));
addr.s_addr = 0;
broadcast.s_addr = 0;
while (RTA_OK(rta, len1)) {
if (rta->rta_type == IFA_LOCAL)
addr = *((struct in_addr*) (rta + 1));
else if (rta->rta_type == IFA_BROADCAST)
broadcast = *((struct in_addr*) (rta + 1));
rta = RTA_NEXT(rta, len1);
}
if (addr.s_addr && ipv4_callback)
if (!((*ipv4_callback)(addr, ifa->ifa_index, netmask, broadcast, parm)))
return 0;
}
#ifdef HAVE_IPV6
else if (ifa->ifa_family == AF_INET6) {
struct in6_addr* addrp = NULL;
while (RTA_OK(rta, len1)) {
if (rta->rta_type == IFA_ADDRESS) addrp = ((struct in6_addr*) (rta + 1));
rta = RTA_NEXT(rta, len1);
}
if (addrp && ipv6_callback)
if (!((*ipv6_callback)(addrp, ifa->ifa_index, ifa->ifa_index, parm)))
return 0;
}
#endif
}
}
}
void netlink_multicast(void) {
ssize_t len;
struct nlmsghdr* h;
int flags;
/* don't risk blocking reading netlink messages here. */
if ((flags = fcntl(daemon->netlinkfd, F_GETFL)) == -1 ||
fcntl(daemon->netlinkfd, F_SETFL, flags | O_NONBLOCK) == -1)
return;
if ((len = netlink_recv()) != -1) {
for (h = (struct nlmsghdr*) iov.iov_base; NLMSG_OK(h, (size_t) len); h = NLMSG_NEXT(h, len))
if (h->nlmsg_type == NLMSG_ERROR)
nl_err(h);
else
nl_routechange(h);
}
/* restore non-blocking status */
fcntl(daemon->netlinkfd, F_SETFL, flags);
}
static void nl_err(struct nlmsghdr* h) {
struct nlmsgerr* err = NLMSG_DATA(h);
if (err->error != 0)
my_syslog(LOG_ERR, _("netlink returns error: %s"), strerror(-(err->error)));
}
/* We arrange to receive netlink multicast messages whenever the network route is added.
If this happens and we still have a DNS packet in the buffer, we re-send it.
This helps on DoD links, where frequently the packet which triggers dialling is
a DNS query, which then gets lost. By re-sending, we can avoid the lookup
failing. Note that we only accept these messages from the kernel (pid == 0) */
static void nl_routechange(struct nlmsghdr* h) {
if (h->nlmsg_pid == 0 && h->nlmsg_type == RTM_NEWROUTE) {
struct rtmsg* rtm = NLMSG_DATA(h);
int fd;
if (rtm->rtm_type != RTN_UNICAST || rtm->rtm_scope != RT_SCOPE_LINK) return;
/* Force re-reading resolv file right now, for luck. */
daemon->last_resolv = 0;
if (daemon->srv_save) {
if (daemon->srv_save->sfd)
fd = daemon->srv_save->sfd->fd;
else if (daemon->rfd_save && daemon->rfd_save->refcount != 0)
fd = daemon->rfd_save->fd;
else
return;
while (sendto(fd, daemon->packet, daemon->packet_len, 0, &daemon->srv_save->addr.sa,
sa_len(&daemon->srv_save->addr)) == -1 &&
retry_send())
;
}
}
}
#endif