/* dnsmasq is Copyright (c) 2000-2022 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/types.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
/* Blergh. Radv does this, so that's our excuse. */
#ifndef SOL_NETLINK
#define SOL_NETLINK 270
#endif
#ifndef NETLINK_NO_ENOBUFS
#define NETLINK_NO_ENOBUFS 5
#endif
/* 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
#ifndef NDA_RTA
# define NDA_RTA(r) ((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct ndmsg))))
#endif
/* Used to request refresh of addresses or routes just once,
* when multiple changes might be announced. */
enum async_states {
STATE_NEWADDR = (1 << 0),
STATE_NEWROUTE = (1 << 1),
};
static struct iovec iov;
static u32 netlink_pid;
static unsigned nl_async(struct nlmsghdr *h, unsigned state);
static void nl_multicast_state(unsigned state);
char *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 */
addr.nl_groups = RTMGRP_IPV4_ROUTE;
addr.nl_groups |= RTMGRP_IPV4_IFADDR;
addr.nl_groups |= RTMGRP_IPV6_ROUTE;
addr.nl_groups |= RTMGRP_IPV6_IFADDR;
/* 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);
return NULL;
}
static ssize_t netlink_recv(int flags)
{
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, flags | 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, flags)) == -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;
}
/* family = AF_UNSPEC finds ARP table entries.
family = AF_LOCAL finds MAC addresses.
returns 0 on failure, 1 on success, -1 when restart is required
*/
int iface_enumerate(int family, void *parm, int (*callback)())
{
struct sockaddr_nl addr;
struct nlmsghdr *h;
ssize_t len;
static unsigned int seq = 0;
int callback_ok = 1;
unsigned state = 0;
struct {
struct nlmsghdr nlh;
struct rtgenmsg g;
} req;
memset(&req, 0, sizeof(req));
memset(&addr, 0, sizeof(addr));
addr.nl_family = AF_NETLINK;
if (family == AF_UNSPEC)
req.nlh.nlmsg_type = RTM_GETNEIGH;
else if (family == AF_LOCAL)
req.nlh.nlmsg_type = RTM_GETLINK;
else
req.nlh.nlmsg_type = RTM_GETADDR;
req.nlh.nlmsg_len = sizeof(req);
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(retry_send(sendto(daemon->netlinkfd, (void *)&req, sizeof(req), 0,
(struct sockaddr *)&addr, sizeof(addr))));
if (errno != 0)
return 0;
while (1)
{
if ((len = netlink_recv(0)) == -1)
{
if (errno == ENOBUFS)
{
nl_multicast_state(state);
return -1;
}
return 0;
}
for (h = (struct nlmsghdr *)iov.iov_base; NLMSG_OK(h, (size_t)len); h = NLMSG_NEXT(h, len))
if (h->nlmsg_pid != netlink_pid || h->nlmsg_type == NLMSG_ERROR)
{
/* May be multicast arriving async */
state = nl_async(h, state);
}
else if (h->nlmsg_seq != seq)
{
/* May be part of incomplete response to previous request after
ENOBUFS. Drop it. */
continue;
}
else if (h->nlmsg_type == NLMSG_DONE)
return callback_ok;
else if (h->nlmsg_type == RTM_NEWADDR && family != AF_UNSPEC && family != AF_LOCAL)
{
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 == family)
{
if (ifa->ifa_family == AF_INET)
{
struct in_addr netmask, addr, broadcast;
char *label = NULL;
netmask.s_addr = htonl(~(in_addr_t)0 << (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));
else if (rta->rta_type == IFA_LABEL)
label = RTA_DATA(rta);
rta = RTA_NEXT(rta, len1);
}
if (addr.s_addr && callback_ok)
if (!((*callback)(addr, ifa->ifa_index, label, netmask, broadcast, parm)))
callback_ok = 0;
}
else if (ifa->ifa_family == AF_INET6)
{
struct in6_addr *addrp = NULL;
u32 valid = 0, preferred = 0;
int flags = 0;
while (RTA_OK(rta, len1))
{
/*
* Important comment: (from if_addr.h)
* IFA_ADDRESS is prefix address, rather than local interface address.
* It makes no difference for normally configured broadcast interfaces,
* but for point-to-point IFA_ADDRESS is DESTINATION address,
* local address is supplied in IFA_LOCAL attribute.
*/
if (rta->rta_type == IFA_LOCAL)
addrp = ((struct in6_addr *)(rta+1));
else if (rta->rta_type == IFA_ADDRESS && !addrp)
addrp = ((struct in6_addr *)(rta+1));
else if (rta->rta_type == IFA_CACHEINFO)
{
struct ifa_cacheinfo *ifc = (struct ifa_cacheinfo *)(rta+1);
preferred = ifc->ifa_prefered;
valid = ifc->ifa_valid;
}
rta = RTA_NEXT(rta, len1);
}
if (ifa->ifa_flags & IFA_F_TENTATIVE)
flags |= IFACE_TENTATIVE;
if (ifa->ifa_flags & IFA_F_DEPRECATED)
flags |= IFACE_DEPRECATED;
if (!(ifa->ifa_flags & IFA_F_TEMPORARY))
flags |= IFACE_PERMANENT;
if (addrp && callback_ok)
if (!((*callback)(addrp, (int)(ifa->ifa_prefixlen), (int)(ifa->ifa_scope),
(int)(ifa->ifa_index), flags,
(int) preferred, (int)valid, parm)))
callback_ok = 0;
}
}
}
else if (h->nlmsg_type == RTM_NEWNEIGH && family == AF_UNSPEC)
{
struct ndmsg *neigh = NLMSG_DATA(h);
struct rtattr *rta = NDA_RTA(neigh);
unsigned int len1 = h->nlmsg_len - NLMSG_LENGTH(sizeof(*neigh));
size_t maclen = 0;
char *inaddr = NULL, *mac = NULL;
while (RTA_OK(rta, len1))
{
if (rta->rta_type == NDA_DST)
inaddr = (char *)(rta+1);
else if (rta->rta_type == NDA_LLADDR)
{
maclen = rta->rta_len - sizeof(struct rtattr);
mac = (char *)(rta+1);
}
rta = RTA_NEXT(rta, len1);
}
if (!(neigh->ndm_state & (NUD_NOARP | NUD_INCOMPLETE | NUD_FAILED)) &&
inaddr && mac && callback_ok)
if (!((*callback)(neigh->ndm_family, inaddr, mac, maclen, parm)))
callback_ok = 0;
}
#ifdef HAVE_DHCP6
else if (h->nlmsg_type == RTM_NEWLINK && family == AF_LOCAL)
{
struct ifinfomsg *link = NLMSG_DATA(h);
struct rtattr *rta = IFLA_RTA(link);
unsigned int len1 = h->nlmsg_len - NLMSG_LENGTH(sizeof(*link));
char *mac = NULL;
size_t maclen = 0;
while (RTA_OK(rta, len1))
{
if (rta->rta_type == IFLA_ADDRESS)
{
maclen = rta->rta_len - sizeof(struct rtattr);
mac = (char *)(rta+1);
}
rta = RTA_NEXT(rta, len1);
}
if (mac && callback_ok && !((link->ifi_flags & (IFF_LOOPBACK | IFF_POINTOPOINT))) &&
!((*callback)((int)link->ifi_index, (unsigned int)link->ifi_type, mac, maclen, parm)))
callback_ok = 0;
}
#endif
}
}
static void nl_multicast_state(unsigned state)
{
ssize_t len;
struct nlmsghdr *h;
do {
/* don't risk blocking reading netlink messages here. */
while ((len = netlink_recv(MSG_DONTWAIT)) != -1)
for (h = (struct nlmsghdr *)iov.iov_base; NLMSG_OK(h, (size_t)len); h = NLMSG_NEXT(h, len))
state = nl_async(h, state);
} while (errno == ENOBUFS);
}
void netlink_multicast(void)
{
unsigned state = 0;
nl_multicast_state(state);
}
static unsigned nl_async(struct nlmsghdr *h, unsigned state)
{
if (h->nlmsg_type == NLMSG_ERROR)
{
struct nlmsgerr *err = NLMSG_DATA(h);
if (err->error != 0)
my_syslog(LOG_ERR, _("netlink returns error: %s"), strerror(-(err->error)));
}
else if (h->nlmsg_pid == 0 && h->nlmsg_type == RTM_NEWROUTE &&
(state & STATE_NEWROUTE)==0)
{
/* 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. */
struct rtmsg *rtm = NLMSG_DATA(h);
if (rtm->rtm_type == RTN_UNICAST && rtm->rtm_scope == RT_SCOPE_LINK &&
(rtm->rtm_table == RT_TABLE_MAIN ||
rtm->rtm_table == RT_TABLE_LOCAL))
{
queue_event(EVENT_NEWROUTE);
state |= STATE_NEWROUTE;
}
}
else if ((h->nlmsg_type == RTM_NEWADDR || h->nlmsg_type == RTM_DELADDR) &&
(state & STATE_NEWADDR)==0)
{
queue_event(EVENT_NEWADDR);
state |= STATE_NEWADDR;
}
return state;
}
#endif /* HAVE_LINUX_NETWORK */
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