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libnetlink.c
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libnetlink.c
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#include <linux/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <libnl3/netlink/attr.h>
#include <libnl3/netlink/msg.h>
#include <string.h>
#include <unistd.h>
#include "libnetlink.h"
#include "util.h"
static int nlmsg_receive(char *buf, int len, int (*cb)(struct nlmsghdr *, void *),
int (*err_cb)(int, void *), void *arg)
{
struct nlmsghdr *hdr;
for (hdr = (struct nlmsghdr *)buf; NLMSG_OK(hdr, len); hdr = NLMSG_NEXT(hdr, len)) {
if (hdr->nlmsg_seq != CR_NLMSG_SEQ)
continue;
if (hdr->nlmsg_type == NLMSG_DONE) {
int *len = (int *)NLMSG_DATA(hdr);
if (*len < 0) {
pr_err("ERROR %d reported by netlink (%s)\n",
*len, strerror(-*len));
return *len;
}
return 0;
}
if (hdr->nlmsg_type == NLMSG_ERROR) {
struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(hdr);
if (hdr->nlmsg_len - sizeof(*hdr) < sizeof(struct nlmsgerr)) {
pr_err("ERROR truncated\n");
return -1;
}
if (err->error == 0)
return 0;
return err_cb(err->error, arg);
}
if (cb(hdr, arg))
return -1;
}
return 1;
}
static int rtnl_return_err(int err, void *arg)
{
pr_warn("ERROR %d reported by netlink\n", err);
return err;
}
int do_rtnl_req(int nl, void *req, int size,
int (*receive_callback)(struct nlmsghdr *h, void *),
int (*error_callback)(int err, void *), void *arg)
{
struct msghdr msg;
struct sockaddr_nl nladdr;
struct iovec iov;
static char buf[16384];
int err;
if (!error_callback)
error_callback = rtnl_return_err;
memset(&msg, 0, sizeof(msg));
msg.msg_name = &nladdr;
msg.msg_namelen = sizeof(nladdr);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
memset(&nladdr, 0, sizeof(nladdr));
nladdr.nl_family = AF_NETLINK;
iov.iov_base = req;
iov.iov_len = size;
if (sendmsg(nl, &msg, 0) < 0) {
err = -errno;
pr_perror("Can't send request message");
goto err;
}
iov.iov_base = buf;
iov.iov_len = sizeof(buf);
while (1) {
memset(&msg, 0, sizeof(msg));
msg.msg_name = &nladdr;
msg.msg_namelen = sizeof(nladdr);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
err = recvmsg(nl, &msg, 0);
if (err < 0) {
if (errno == EINTR)
continue;
else {
err = -errno;
pr_perror("Error receiving nl report");
goto err;
}
}
if (err == 0)
break;
if (msg.msg_flags & MSG_TRUNC) {
pr_err("Message truncated\n");
err = -EMSGSIZE;
goto err;
}
err = nlmsg_receive(buf, err, receive_callback, error_callback, arg);
if (err < 0)
goto err;
if (err == 0)
break;
}
return 0;
err:
return err;
}
int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
int alen)
{
int len = nla_attr_size(alen);
struct rtattr *rta;
if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
pr_err("addattr_l ERROR: message exceeded bound of %d\n", maxlen);
return -1;
}
rta = NLMSG_TAIL(n);
rta->rta_type = type;
rta->rta_len = len;
memcpy(RTA_DATA(rta), data, alen);
n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
return 0;
}
/*
* Here is a workaround for a bug in libnl-3:
* 6a8d90f5fec4 "attr: Allow attribute type 0
*/
/**
* Create attribute index based on a stream of attributes.
* @arg tb Index array to be filled (maxtype+1 elements).
* @arg maxtype Maximum attribute type expected and accepted.
* @arg head Head of attribute stream.
* @arg len Length of attribute stream.
* @arg policy Attribute validation policy.
*
* Iterates over the stream of attributes and stores a pointer to each
* attribute in the index array using the attribute type as index to
* the array. Attribute with a type greater than the maximum type
* specified will be silently ignored in order to maintain backwards
* compatibility. If \a policy is not NULL, the attribute will be
* validated using the specified policy.
*
* @see nla_validate
* @return 0 on success or a negative error code.
*/
int __wrap_nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
struct nla_policy *policy)
{
struct nlattr *nla;
int rem;
memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
nla_for_each_attr(nla, head, len, rem) {
int type = nla_type(nla);
if (type > maxtype)
continue;
if (tb[type])
pr_warn("Attribute of type %#x found multiple times in message, "
"previous attribute is being ignored.\n", type);
tb[type] = nla;
}
if (rem > 0)
pr_warn("netlink: %d bytes leftover after parsing "
"attributes.\n", rem);
return 0;
}
/**
* parse attributes of a netlink message
* @arg nlh netlink message header
* @arg hdrlen length of family specific header
* @arg tb destination array with maxtype+1 elements
* @arg maxtype maximum attribute type to be expected
* @arg policy validation policy
*
* See nla_parse()
*/
int __wrap_nlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
int maxtype, struct nla_policy *policy)
{
if (!nlmsg_valid_hdr(nlh, hdrlen))
return -NLE_MSG_TOOSHORT;
return nla_parse(tb, maxtype, nlmsg_attrdata(nlh, hdrlen),
nlmsg_attrlen(nlh, hdrlen), policy);
}