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// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <stdint.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <unistd.h>
#include <linux/genetlink.h>
#include "netlink_helper.h"
int netlink_open(void)
{
struct timeval tv = { .tv_sec = ACCT_RCV_TIMEOUT_SEC };
struct sockaddr_nl addr = {
.nl_family = AF_NETLINK,
.nl_pid = getpid(),
};
int fd;
fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
if (fd < 0)
return -errno;
if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) {
int err = -errno;
close(fd);
return err;
}
if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
int err = -errno;
close(fd);
return err;
}
return fd;
}
int send_request(int fd, void *buf, size_t len)
{
struct sockaddr_nl addr = {
.nl_family = AF_NETLINK,
};
if (sendto(fd, buf, len, 0, (struct sockaddr *)&addr, sizeof(addr)) < 0)
return -errno;
return 0;
}
/*
* Resolve the generic netlink family ID for @name.
* Returns the family ID (>= 0) on success, negative errno on failure.
*/
int get_family_id(int fd, const char *name)
{
struct {
struct nlmsghdr nlh;
struct genlmsghdr genl;
char buf[256];
} req = { 0 };
char resp[8192];
struct nlmsghdr *nlh;
struct genlmsghdr *genl;
struct nlattr *na;
int len;
int rem;
int ret;
req.nlh.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
req.nlh.nlmsg_type = GENL_ID_CTRL;
req.nlh.nlmsg_flags = NLM_F_REQUEST;
req.nlh.nlmsg_seq = 1;
req.nlh.nlmsg_pid = getpid();
req.genl.cmd = CTRL_CMD_GETFAMILY;
req.genl.version = 1;
na = (struct nlattr *)((char *)&req + NLMSG_ALIGN(req.nlh.nlmsg_len));
na->nla_type = CTRL_ATTR_FAMILY_NAME;
na->nla_len = NLA_HDRLEN + strlen(name) + 1;
memcpy(nla_data(na), name, strlen(name) + 1);
req.nlh.nlmsg_len = NLMSG_ALIGN(req.nlh.nlmsg_len) + NLA_ALIGN(na->nla_len);
ret = send_request(fd, &req, req.nlh.nlmsg_len);
if (ret)
return ret;
len = recv(fd, resp, sizeof(resp), 0);
if (len < 0)
return -errno;
for (nlh = (struct nlmsghdr *)resp; NLMSG_OK(nlh, len);
nlh = NLMSG_NEXT(nlh, len)) {
if (nlh->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = NLMSG_DATA(nlh);
return err->error ? err->error : -ENOENT;
}
genl = (struct genlmsghdr *)NLMSG_DATA(nlh);
rem = nlh->nlmsg_len - NLMSG_HDRLEN - GENL_HDRLEN;
na = (struct nlattr *)((char *)genl + GENL_HDRLEN);
while (nla_ok(na, rem)) {
if (na->nla_type == CTRL_ATTR_FAMILY_ID)
return *(uint16_t *)nla_data(na);
na = nla_next(na, &rem);
}
}
return -ENOENT;
}
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