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busybox/networking/libiproute/libnetlink.c
Hauke Mehrtens 4ff86df861 libnetlink: fix alignment of netlink messages 
A padding to align a message should not only be added between
different attributes of a netlink message, but also at the end of the
message to pad it to the correct size.

Without this patch the following command does not work and returns an
error code:
ip link add type nlmon

Without this ip from busybox sends this:

sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000},
	msg_namelen=12, msg_iov=[{iov_base={{len=45, ...},
		"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\0\22\0\t\0\1nlmon"}, iov_len=45}],
	msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 45
return value: 2

The normal ip utile from iproute2 sends this:

sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000},
	msg_namelen=12, msg_iov=[{iov_base={{len=48, ...},
		"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\0\22\0\t\0\1nlmon\0\0\0"}, iov_len=48}],
	msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 48
return value: 0

With this patch ip from busybox sends this:

sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000},
	msg_namelen=12, msg_iov=[{iov_base={{len=48, ...},
		"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\0\22\0\t\0\1nlmon\0\0\0"}, iov_len=48}],
	msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 48
return value: 0

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-09-18 22:55:47 +02:00

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/* vi: set sw=4 ts=4: */
/*
* 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; either version
* 2 of the License, or (at your option) any later version.
*
* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
*/
#include <sys/socket.h>
#include <sys/uio.h>
#include "libbb.h"
#include "libnetlink.h"
void FAST_FUNC xrtnl_open(struct rtnl_handle *rth/*, unsigned subscriptions*/)
{
socklen_t addr_len;
memset(rth, 0, sizeof(*rth));
rth->fd = xsocket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
rth->local.nl_family = AF_NETLINK;
/*rth->local.nl_groups = subscriptions;*/
xbind(rth->fd, (struct sockaddr*)&rth->local, sizeof(rth->local));
addr_len = sizeof(rth->local);
getsockname(rth->fd, (struct sockaddr*)&rth->local, &addr_len);
/* too much paranoia
if (getsockname(rth->fd, (struct sockaddr*)&rth->local, &addr_len) < 0)
bb_perror_msg_and_die("getsockname");
if (addr_len != sizeof(rth->local))
bb_error_msg_and_die("wrong address length %d", addr_len);
if (rth->local.nl_family != AF_NETLINK)
bb_error_msg_and_die("wrong address family %d", rth->local.nl_family);
*/
rth->seq = time(NULL);
}
int FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
{
struct {
struct nlmsghdr nlh;
struct rtgenmsg g;
} req;
req.nlh.nlmsg_len = sizeof(req);
req.nlh.nlmsg_type = type;
req.nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
req.nlh.nlmsg_pid = 0;
req.nlh.nlmsg_seq = rth->dump = ++rth->seq;
req.g.rtgen_family = family;
return rtnl_send(rth, (void*)&req, sizeof(req));
}
//TODO: pass rth->fd instead of full rth?
int FAST_FUNC rtnl_send(struct rtnl_handle *rth, char *buf, int len)
{
struct sockaddr_nl nladdr;
memset(&nladdr, 0, sizeof(nladdr));
nladdr.nl_family = AF_NETLINK;
return xsendto(rth->fd, buf, len, (struct sockaddr*)&nladdr, sizeof(nladdr));
}
int FAST_FUNC rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)
{
struct {
struct nlmsghdr nlh;
struct msghdr msg;
struct sockaddr_nl nladdr;
} s;
struct iovec iov[2] = { { &s.nlh, sizeof(s.nlh) }, { req, len } };
memset(&s, 0, sizeof(s));
s.msg.msg_name = (void*)&s.nladdr;
s.msg.msg_namelen = sizeof(s.nladdr);
s.msg.msg_iov = iov;
s.msg.msg_iovlen = 2;
/*s.msg.msg_control = NULL; - already is */
/*s.msg.msg_controllen = 0; - already is */
/*s.msg.msg_flags = 0; - already is */
s.nladdr.nl_family = AF_NETLINK;
s.nlh.nlmsg_len = NLMSG_LENGTH(len);
s.nlh.nlmsg_type = type;
s.nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
/*s.nlh.nlmsg_pid = 0; - already is */
s.nlh.nlmsg_seq = rth->dump = ++rth->seq;
return sendmsg(rth->fd, &s.msg, 0);
}
static int rtnl_dump_filter(struct rtnl_handle *rth,
int (*filter)(const struct sockaddr_nl *, struct nlmsghdr *n, void *) FAST_FUNC,
void *arg1/*,
int (*junk)(struct sockaddr_nl *, struct nlmsghdr *n, void *),
void *arg2*/)
{
int retval = -1;
char *buf = xmalloc(8*1024); /* avoid big stack buffer */
struct sockaddr_nl nladdr;
struct iovec iov = { buf, 8*1024 };
while (1) {
int status;
struct nlmsghdr *h;
/* Use designated initializers, struct layout is non-portable */
struct msghdr msg = {
.msg_name = (void*)&nladdr,
.msg_namelen = sizeof(nladdr),
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = NULL,
.msg_controllen = 0,
.msg_flags = 0
};
status = recvmsg(rth->fd, &msg, 0);
if (status < 0) {
if (errno == EINTR)
continue;
bb_perror_msg("OVERRUN");
continue;
}
if (status == 0) {
bb_error_msg("EOF on netlink");
goto ret;
}
if (msg.msg_namelen != sizeof(nladdr)) {
bb_error_msg_and_die("sender address length == %d", msg.msg_namelen);
}
h = (struct nlmsghdr*)buf;
while (NLMSG_OK(h, status)) {
int err;
if (nladdr.nl_pid != 0 ||
h->nlmsg_pid != rth->local.nl_pid ||
h->nlmsg_seq != rth->dump
) {
// if (junk) {
// err = junk(&nladdr, h, arg2);
// if (err < 0) {
// retval = err;
// goto ret;
// }
// }
goto skip_it;
}
if (h->nlmsg_type == NLMSG_DONE) {
goto ret_0;
}
if (h->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *l_err = (struct nlmsgerr*)NLMSG_DATA(h);
if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr))) {
bb_error_msg("ERROR truncated");
} else {
errno = -l_err->error;
bb_perror_msg("RTNETLINK answers");
}
goto ret;
}
err = filter(&nladdr, h, arg1);
if (err < 0) {
retval = err;
goto ret;
}
skip_it:
h = NLMSG_NEXT(h, status);
}
if (msg.msg_flags & MSG_TRUNC) {
bb_error_msg("message truncated");
continue;
}
if (status) {
bb_error_msg_and_die("remnant of size %d!", status);
}
} /* while (1) */
ret_0:
retval++; /* = 0 */
ret:
free(buf);
return retval;
}
int FAST_FUNC xrtnl_dump_filter(struct rtnl_handle *rth,
int (*filter)(const struct sockaddr_nl *, struct nlmsghdr *, void *) FAST_FUNC,
void *arg1)
{
int ret = rtnl_dump_filter(rth, filter, arg1/*, NULL, NULL*/);
if (ret < 0)
bb_error_msg_and_die("dump terminated");
return ret;
}
int FAST_FUNC rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
pid_t peer, unsigned groups,
struct nlmsghdr *answer,
int (*junk)(struct sockaddr_nl *, struct nlmsghdr *, void *),
void *jarg)
{
/* bbox doesn't use parameters no. 3, 4, 6, 7, they are stubbed out */
#define peer 0
#define groups 0
#define junk NULL
#define jarg NULL
int retval = -1;
int status;
unsigned seq;
struct nlmsghdr *h;
struct sockaddr_nl nladdr;
struct iovec iov = { (void*)n, n->nlmsg_len };
char *buf = xmalloc(8*1024); /* avoid big stack buffer */
/* Use designated initializers, struct layout is non-portable */
struct msghdr msg = {
.msg_name = (void*)&nladdr,
.msg_namelen = sizeof(nladdr),
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = NULL,
.msg_controllen = 0,
.msg_flags = 0
};
memset(&nladdr, 0, sizeof(nladdr));
nladdr.nl_family = AF_NETLINK;
// nladdr.nl_pid = peer;
// nladdr.nl_groups = groups;
n->nlmsg_seq = seq = ++rtnl->seq;
if (answer == NULL) {
n->nlmsg_flags |= NLM_F_ACK;
}
status = sendmsg(rtnl->fd, &msg, 0);
if (status < 0) {
bb_perror_msg("can't talk to rtnetlink");
goto ret;
}
iov.iov_base = buf;
while (1) {
iov.iov_len = 8*1024;
status = recvmsg(rtnl->fd, &msg, 0);
if (status < 0) {
if (errno == EINTR) {
continue;
}
bb_perror_msg("OVERRUN");
continue;
}
if (status == 0) {
bb_error_msg("EOF on netlink");
goto ret;
}
if (msg.msg_namelen != sizeof(nladdr)) {
bb_error_msg_and_die("sender address length == %d", msg.msg_namelen);
}
for (h = (struct nlmsghdr*)buf; status >= (int)sizeof(*h); ) {
// int l_err;
int len = h->nlmsg_len;
int l = len - sizeof(*h);
if (l < 0 || len > status) {
if (msg.msg_flags & MSG_TRUNC) {
bb_error_msg("truncated message");
goto ret;
}
bb_error_msg_and_die("malformed message: len=%d!", len);
}
if (nladdr.nl_pid != peer ||
h->nlmsg_pid != rtnl->local.nl_pid ||
h->nlmsg_seq != seq
) {
// if (junk) {
// l_err = junk(&nladdr, h, jarg);
// if (l_err < 0) {
// retval = l_err;
// goto ret;
// }
// }
continue;
}
if (h->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h);
if (l < (int)sizeof(struct nlmsgerr)) {
bb_error_msg("ERROR truncated");
} else {
errno = - err->error;
if (errno == 0) {
if (answer) {
memcpy(answer, h, h->nlmsg_len);
}
goto ret_0;
}
bb_perror_msg("RTNETLINK answers");
}
goto ret;
}
if (answer) {
memcpy(answer, h, h->nlmsg_len);
goto ret_0;
}
bb_error_msg("unexpected reply!");
status -= NLMSG_ALIGN(len);
h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len));
}
if (msg.msg_flags & MSG_TRUNC) {
bb_error_msg("message truncated");
continue;
}
if (status) {
bb_error_msg_and_die("remnant of size %d!", status);
}
} /* while (1) */
ret_0:
retval++; /* = 0 */
ret:
free(buf);
return retval;
}
int FAST_FUNC addattr32(struct nlmsghdr *n, int maxlen, int type, uint32_t data)
{
int len = RTA_LENGTH(4);
struct rtattr *rta;
if ((int)(NLMSG_ALIGN(n->nlmsg_len + len)) > maxlen) {
return -1;
}
rta = (struct rtattr*)(((char*)n) + NLMSG_ALIGN(n->nlmsg_len));
rta->rta_type = type;
rta->rta_len = len;
move_to_unaligned32(RTA_DATA(rta), data);
n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len + len);
return 0;
}
int FAST_FUNC addattr_l(struct nlmsghdr *n, int maxlen, int type, void *data, int alen)
{
int len = RTA_LENGTH(alen);
struct rtattr *rta;
if ((int)(NLMSG_ALIGN(n->nlmsg_len + len)) > maxlen) {
return -1;
}
rta = (struct rtattr*)(((char*)n) + NLMSG_ALIGN(n->nlmsg_len));
rta->rta_type = type;
rta->rta_len = len;
memcpy(RTA_DATA(rta), data, alen);
n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len + len);
return 0;
}
int FAST_FUNC rta_addattr32(struct rtattr *rta, int maxlen, int type, uint32_t data)
{
int len = RTA_LENGTH(4);
struct rtattr *subrta;
if (RTA_ALIGN(rta->rta_len + len) > maxlen) {
return -1;
}
subrta = (struct rtattr*)(((char*)rta) + RTA_ALIGN(rta->rta_len));
subrta->rta_type = type;
subrta->rta_len = len;
move_to_unaligned32(RTA_DATA(subrta), data);
rta->rta_len = NLMSG_ALIGN(rta->rta_len + len);
return 0;
}
int FAST_FUNC rta_addattr_l(struct rtattr *rta, int maxlen, int type, void *data, int alen)
{
struct rtattr *subrta;
int len = RTA_LENGTH(alen);
if (RTA_ALIGN(rta->rta_len + len) > maxlen) {
return -1;
}
subrta = (struct rtattr*)(((char*)rta) + RTA_ALIGN(rta->rta_len));
subrta->rta_type = type;
subrta->rta_len = len;
memcpy(RTA_DATA(subrta), data, alen);
rta->rta_len = NLMSG_ALIGN(rta->rta_len + len);
return 0;
}
void FAST_FUNC parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len)
{
while (RTA_OK(rta, len)) {
if (rta->rta_type <= max) {
tb[rta->rta_type] = rta;
}
rta = RTA_NEXT(rta, len);
}
if (len) {
bb_error_msg("deficit %d, rta_len=%d!", len, rta->rta_len);
}
}
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