// SPDX-License-Identifier: GPL-2.0-or-later
/* Taken & modified from iproute2's libnetlink.c
* Authors: Alexey Kuznetsov, <[email protected]>
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <sys/socket.h>
#include "netlink_helpers.h"
static int rcvbuf = 1024 * 1024;
void rtnl_close(struct rtnl_handle *rth)
{
if (rth->fd >= 0) {
close(rth->fd);
rth->fd = -1;
}
}
int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int subscriptions,
int protocol)
{
socklen_t addr_len;
int sndbuf = 32768;
int one = 1;
memset(rth, 0, sizeof(*rth));
rth->proto = protocol;
rth->fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, protocol);
if (rth->fd < 0) {
perror("Cannot open netlink socket");
return -1;
}
if (setsockopt(rth->fd, SOL_SOCKET, SO_SNDBUF,
&sndbuf, sizeof(sndbuf)) < 0) {
perror("SO_SNDBUF");
goto err;
}
if (setsockopt(rth->fd, SOL_SOCKET, SO_RCVBUF,
&rcvbuf, sizeof(rcvbuf)) < 0) {
perror("SO_RCVBUF");
goto err;
}
/* Older kernels may no support extended ACK reporting */
setsockopt(rth->fd, SOL_NETLINK, NETLINK_EXT_ACK,
&one, sizeof(one));
memset(&rth->local, 0, sizeof(rth->local));
rth->local.nl_family = AF_NETLINK;
rth->local.nl_groups = subscriptions;
if (bind(rth->fd, (struct sockaddr *)&rth->local,
sizeof(rth->local)) < 0) {
perror("Cannot bind netlink socket");
goto err;
}
addr_len = sizeof(rth->local);
if (getsockname(rth->fd, (struct sockaddr *)&rth->local,
&addr_len) < 0) {
perror("Cannot getsockname");
goto err;
}
if (addr_len != sizeof(rth->local)) {
fprintf(stderr, "Wrong address length %d\n", addr_len);
goto err;
}
if (rth->local.nl_family != AF_NETLINK) {
fprintf(stderr, "Wrong address family %d\n",
rth->local.nl_family);
goto err;
}
rth->seq = time(NULL);
return 0;
err:
rtnl_close(rth);
return -1;
}
int rtnl_open(struct rtnl_handle *rth, unsigned int subscriptions)
{
return rtnl_open_byproto(rth, subscriptions, NETLINK_ROUTE);
}
static int __rtnl_recvmsg(int fd, struct msghdr *msg, int flags)
{
int len;
do {
len = recvmsg(fd, msg, flags);
} while (len < 0 && (errno == EINTR || errno == EAGAIN));
if (len < 0) {
fprintf(stderr, "netlink receive error %s (%d)\n",
strerror(errno), errno);
return -errno;
}
if (len == 0) {
fprintf(stderr, "EOF on netlink\n");
return -ENODATA;
}
return len;
}
static int rtnl_recvmsg(int fd, struct msghdr *msg, char **answer)
{
struct iovec *iov = msg->msg_iov;
char *buf;
int len;
iov->iov_base = NULL;
iov->iov_len = 0;
len = __rtnl_recvmsg(fd, msg, MSG_PEEK | MSG_TRUNC);
if (len < 0)
return len;
if (len < 32768)
len = 32768;
buf = malloc(len);
if (!buf) {
fprintf(stderr, "malloc error: not enough buffer\n");
return -ENOMEM;
}
iov->iov_base = buf;
iov->iov_len = len;
len = __rtnl_recvmsg(fd, msg, 0);
if (len < 0) {
free(buf);
return len;
}
if (answer)
*answer = buf;
else
free(buf);
return len;
}
static void rtnl_talk_error(struct nlmsghdr *h, struct nlmsgerr *err,
nl_ext_ack_fn_t errfn)
{
fprintf(stderr, "RTNETLINK answers: %s\n",
strerror(-err->error));
}
static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iov,
size_t iovlen, struct nlmsghdr **answer,
bool show_rtnl_err, nl_ext_ack_fn_t errfn)
{
struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
struct iovec riov;
struct msghdr msg = {
.msg_name = &nladdr,
.msg_namelen = sizeof(nladdr),
.msg_iov = iov,
.msg_iovlen = iovlen,
};
unsigned int seq = 0;
struct nlmsghdr *h;
int i, status;
char *buf;
for (i = 0; i < iovlen; i++) {
h = iov[i].iov_base;
h->nlmsg_seq = seq = ++rtnl->seq;
if (answer == NULL)
h->nlmsg_flags |= NLM_F_ACK;
}
status = sendmsg(rtnl->fd, &msg, 0);
if (status < 0) {
perror("Cannot talk to rtnetlink");
return -1;
}
/* change msg to use the response iov */
msg.msg_iov = &riov;
msg.msg_iovlen = 1;
i = 0;
while (1) {
next:
status = rtnl_recvmsg(rtnl->fd, &msg, &buf);
++i;
if (status < 0)
return status;
if (msg.msg_namelen != sizeof(nladdr)) {
fprintf(stderr,
"Sender address length == %d!\n",
msg.msg_namelen);
exit(1);
}
for (h = (struct nlmsghdr *)buf; status >= sizeof(*h); ) {
int len = h->nlmsg_len;
int l = len - sizeof(*h);
if (l < 0 || len > status) {
if (msg.msg_flags & MSG_TRUNC) {
fprintf(stderr, "Truncated message!\n");
free(buf);
return -1;
}
fprintf(stderr,
"Malformed message: len=%d!\n",
len);
exit(1);
}
if (nladdr.nl_pid != 0 ||
h->nlmsg_pid != rtnl->local.nl_pid ||
h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
/* Don't forget to skip that message. */
status -= NLMSG_ALIGN(len);
h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
continue;
}
if (h->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);
int error = err->error;
if (l < sizeof(struct nlmsgerr)) {
fprintf(stderr, "ERROR truncated\n");
free(buf);
return -1;
}
if (error) {
errno = -error;
if (rtnl->proto != NETLINK_SOCK_DIAG &&
show_rtnl_err)
rtnl_talk_error(h, err, errfn);
}
if (i < iovlen) {
free(buf);
goto next;
}
if (error) {
free(buf);
return -i;
}
if (answer)
*answer = (struct nlmsghdr *)buf;
else
free(buf);
return 0;
}
if (answer) {
*answer = (struct nlmsghdr *)buf;
return 0;
}
fprintf(stderr, "Unexpected reply!\n");
status -= NLMSG_ALIGN(len);
h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
}
free(buf);
if (msg.msg_flags & MSG_TRUNC) {
fprintf(stderr, "Message truncated!\n");
continue;
}
if (status) {
fprintf(stderr, "Remnant of size %d!\n", status);
exit(1);
}
}
}
static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
struct nlmsghdr **answer, bool show_rtnl_err,
nl_ext_ack_fn_t errfn)
{
struct iovec iov = {
.iov_base = n,
.iov_len = n->nlmsg_len,
};
return __rtnl_talk_iov(rtnl, &iov, 1, answer, show_rtnl_err, errfn);
}
int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
struct nlmsghdr **answer)
{
return __rtnl_talk(rtnl, n, answer, true, NULL);
}
int addattr(struct nlmsghdr *n, int maxlen, int type)
{
return addattr_l(n, maxlen, type, NULL, 0);
}
int addattr8(struct nlmsghdr *n, int maxlen, int type, __u8 data)
{
return addattr_l(n, maxlen, type, &data, sizeof(__u8));
}
int addattr16(struct nlmsghdr *n, int maxlen, int type, __u16 data)
{
return addattr_l(n, maxlen, type, &data, sizeof(__u16));
}
int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data)
{
return addattr_l(n, maxlen, type, &data, sizeof(__u32));
}
int addattr64(struct nlmsghdr *n, int maxlen, int type, __u64 data)
{
return addattr_l(n, maxlen, type, &data, sizeof(__u64));
}
int addattrstrz(struct nlmsghdr *n, int maxlen, int type, const char *str)
{
return addattr_l(n, maxlen, type, str, strlen(str)+1);
}
int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
int alen)
{
int len = RTA_LENGTH(alen);
struct rtattr *rta;
if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
fprintf(stderr, "%s: Message exceeded bound of %d\n",
__func__, maxlen);
return -1;
}
rta = NLMSG_TAIL(n);
rta->rta_type = type;
rta->rta_len = len;
if (alen)
memcpy(RTA_DATA(rta), data, alen);
n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
return 0;
}
int addraw_l(struct nlmsghdr *n, int maxlen, const void *data, int len)
{
if (NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len) > maxlen) {
fprintf(stderr, "%s: Message exceeded bound of %d\n",
__func__, maxlen);
return -1;
}
memcpy(NLMSG_TAIL(n), data, len);
memset((void *) NLMSG_TAIL(n) + len, 0, NLMSG_ALIGN(len) - len);
n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len);
return 0;
}
struct rtattr *addattr_nest(struct nlmsghdr *n, int maxlen, int type)
{
struct rtattr *nest = NLMSG_TAIL(n);
addattr_l(n, maxlen, type, NULL, 0);
return nest;
}
int addattr_nest_end(struct nlmsghdr *n, struct rtattr *nest)
{
nest->rta_len = (void *)NLMSG_TAIL(n) - (void *)nest;
return n->nlmsg_len;
}
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