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/* Netlink helpers for zbuf
* Copyright (c) 2014-2015 Timo Teräs
*
* This file is free software: you may copy, redistribute and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*/
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include "znl.h"
#define ZNL_ALIGN(len) (((len)+3) & ~3)
void *znl_push(struct zbuf *zb, size_t n)
{
return zbuf_pushn(zb, ZNL_ALIGN(n));
}
void *znl_pull(struct zbuf *zb, size_t n)
{
return zbuf_pulln(zb, ZNL_ALIGN(n));
}
struct nlmsghdr *znl_nlmsg_push(struct zbuf *zb, uint16_t type, uint16_t flags)
{
struct nlmsghdr *n;
n = znl_push(zb, sizeof(*n));
if (!n) return NULL;
*n = (struct nlmsghdr) {
.nlmsg_type = type,
.nlmsg_flags = flags,
};
return n;
}
void znl_nlmsg_complete(struct zbuf *zb, struct nlmsghdr *n)
{
n->nlmsg_len = zb->tail - (uint8_t*)n;
}
struct nlmsghdr *znl_nlmsg_pull(struct zbuf *zb, struct zbuf *payload)
{
struct nlmsghdr *n;
size_t plen;
n = znl_pull(zb, sizeof(*n));
if (!n) return NULL;
plen = n->nlmsg_len - sizeof(*n);
zbuf_init(payload, znl_pull(zb, plen), plen, plen);
zbuf_may_pulln(zb, ZNL_ALIGN(plen) - plen);
return n;
}
struct rtattr *znl_rta_push(struct zbuf *zb, uint16_t type, const void *val, size_t len)
{
struct rtattr *rta;
uint8_t *dst;
rta = znl_push(zb, ZNL_ALIGN(sizeof(*rta)) + ZNL_ALIGN(len));
if (!rta) return NULL;
*rta = (struct rtattr) {
.rta_type = type,
.rta_len = ZNL_ALIGN(sizeof(*rta)) + len,
};
dst = (uint8_t *)(rta+1);
memcpy(dst, val, len);
memset(dst+len, 0, ZNL_ALIGN(len) - len);
return rta;
}
struct rtattr *znl_rta_push_u32(struct zbuf *zb, uint16_t type, uint32_t val)
{
return znl_rta_push(zb, type, &val, sizeof(val));
}
struct rtattr *znl_rta_nested_push(struct zbuf *zb, uint16_t type)
{
struct rtattr *rta;
rta = znl_push(zb, sizeof(*rta));
if (!rta) return NULL;
*rta = (struct rtattr) {
.rta_type = type,
};
return rta;
}
void znl_rta_nested_complete(struct zbuf *zb, struct rtattr *rta)
{
size_t len = zb->tail - (uint8_t*) rta;
size_t align = ZNL_ALIGN(len) - len;
if (align) {
void *dst = zbuf_pushn(zb, align);
if (dst) memset(dst, 0, align);
}
rta->rta_len = len;
}
struct rtattr *znl_rta_pull(struct zbuf *zb, struct zbuf *payload)
{
struct rtattr *rta;
size_t plen;
rta = znl_pull(zb, sizeof(*rta));
if (!rta) return NULL;
if (rta->rta_len > sizeof(*rta)) {
plen = rta->rta_len - sizeof(*rta);
zbuf_init(payload, znl_pull(zb, plen), plen, plen);
} else {
zbuf_init(payload, NULL, 0, 0);
}
return rta;
}
int znl_open(int protocol, int groups)
{
struct sockaddr_nl addr;
int fd, buf = 128 * 1024;
fd = socket(AF_NETLINK, SOCK_RAW, protocol);
if (fd < 0)
return -1;
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
fcntl(fd, F_SETFD, FD_CLOEXEC);
if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &buf, sizeof(buf)) < 0)
goto error;
memset(&addr, 0, sizeof(addr));
addr.nl_family = AF_NETLINK;
addr.nl_groups = groups;
if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) < 0)
goto error;
return fd;
error:
close(fd);
return -1;
}
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