summaryrefslogtreecommitdiffstats
path: root/src/netlink.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/netlink.c')
-rwxr-xr-xsrc/netlink.c303
1 files changed, 303 insertions, 0 deletions
diff --git a/src/netlink.c b/src/netlink.c
new file mode 100755
index 0000000..77c4385
--- /dev/null
+++ b/src/netlink.c
@@ -0,0 +1,303 @@
+/* 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/types.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.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
+
+
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-30 16:28:12 +0000