ndhc/netlink.c

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// Copyright 2011-2018 Nicholas J. Kain <njkain at gmail dot com>
// SPDX-License-Identifier: MIT
#include <unistd.h>
#include <arpa/inet.h>
#include <assert.h>
#include <asm/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <stdlib.h>
#include <string.h>
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#include <time.h>
#include <errno.h>
#include <poll.h>
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#include "nk/log.h"
#include "netlink.h"
#include "nl.h"
#include "state.h"
// Returns true if the current interface state is UP.
bool nl_event_carrier_wentup(int state)
{
switch (state) {
case IFS_UP:
log_line("%s: Carrier up.", client_config.interface);
return true;
case IFS_DOWN:
// Interface configured, but no hardware carrier.
log_line("%s: Carrier down.", client_config.interface);
return false;
case IFS_SHUT:
// User shut down the interface.
log_line("%s: Interface shut down.", client_config.interface);
return false;
case IFS_REMOVED:
log_line("Interface removed. Exiting.");
exit(EXIT_SUCCESS);
default: return false;
}
}
static int nl_process_msgs_return;
static void nl_process_msgs(const struct nlmsghdr *nlh, void *data)
{
(void)data;
struct ifinfomsg *ifm = NLMSG_DATA(nlh);
if (ifm->ifi_index != client_config.ifindex)
return;
if (nlh->nlmsg_type == RTM_NEWLINK) {
// IFF_UP corresponds to ifconfig down or ifconfig up.
// IFF_RUNNING is the hardware carrier.
if (ifm->ifi_flags & IFF_UP) {
if (ifm->ifi_flags & IFF_RUNNING)
nl_process_msgs_return = IFS_UP;
else
nl_process_msgs_return = IFS_DOWN;
} else {
nl_process_msgs_return = IFS_SHUT;
}
} else if (nlh->nlmsg_type == RTM_DELLINK)
nl_process_msgs_return = IFS_REMOVED;
}
int nl_event_get(struct client_state_t *cs)
{
char nlbuf[8192];
ssize_t ret;
assert(cs->nlFd != -1);
nl_process_msgs_return = IFS_NONE;
do {
ret = nl_recv_buf(cs->nlFd, nlbuf, sizeof nlbuf);
if (ret < 0)
break;
if (nl_foreach_nlmsg(nlbuf, (size_t)ret, 0, cs->nlPortId, nl_process_msgs, 0) < 0)
break;
} while (ret > 0);
return nl_process_msgs_return;
}
static int get_if_index_and_mac(const struct nlmsghdr *nlh,
struct ifinfomsg *ifm)
{
struct rtattr *tb[IFLA_MAX] = {0};
nl_rtattr_parse(nlh, sizeof *ifm, rtattr_assign, tb);
if (tb[IFLA_IFNAME] && !strncmp(client_config.interface,
RTA_DATA(tb[IFLA_IFNAME]),
sizeof client_config.interface)) {
client_config.ifindex = ifm->ifi_index;
if (!tb[IFLA_ADDRESS])
suicide("FATAL: Adapter %s lacks a hardware address.", client_config.interface);
int maclen = tb[IFLA_ADDRESS]->rta_len - 4;
if (maclen != 6)
suicide("FATAL: Adapter hardware address length should be 6, but is %u.",
maclen);
const unsigned char *mac = RTA_DATA(tb[IFLA_ADDRESS]);
log_line("%s hardware address %x:%x:%x:%x:%x:%x",
client_config.interface,
mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
memcpy(client_config.arp, mac, 6);
return 1;
}
return 0;
}
static void do_handle_getifdata(const struct nlmsghdr *nlh, void *data)
{
int *got_ifdata = (int *)data;
struct ifinfomsg *ifm = NLMSG_DATA(nlh);
switch(nlh->nlmsg_type) {
case RTM_NEWLINK:
*got_ifdata |= get_if_index_and_mac(nlh, ifm);
break;
default:
break;
}
}
static int handle_getifdata(int fd, uint32_t seq)
{
char nlbuf[8192];
ssize_t ret;
int got_ifdata = 0;
do {
ret = nl_recv_buf(fd, nlbuf, sizeof nlbuf);
if (ret < 0)
return -1;
if (nl_foreach_nlmsg(nlbuf, (size_t)ret, seq, 0,
do_handle_getifdata, &got_ifdata) < 0)
return -1;
} while (ret > 0);
return got_ifdata ? 0 : -1;
}
int nl_getifdata(void)
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{
int ret = -1;
int fd = socket(AF_NETLINK, SOCK_DGRAM|SOCK_CLOEXEC, NETLINK_ROUTE);
if (fd < 0) {
log_line("%s: (%s) netlink socket open failed: %s",
client_config.interface, __func__, strerror(errno));
goto fail;
}
struct timespec ts;
if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
log_line("%s: (%s) clock_gettime failed",
client_config.interface, __func__);
goto fail_fd;
}
uint32_t seq = ts.tv_nsec;
if (nl_sendgetlinks(fd, seq)) {
log_line("%s: (%s) nl_sendgetlinks failed",
client_config.interface, __func__);
goto fail_fd;
}
for (int pr = 0; !pr;) {
pr = poll(&((struct pollfd){.fd=fd,.events=POLLIN}), 1, -1);
if (pr == 1)
ret = handle_getifdata(fd, seq);
else if (pr < 0 && errno != EINTR)
goto fail_fd;
}
fail_fd:
close(fd);
fail:
return ret;
}