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