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ovs/lib/netlink-socket.c
Ben Pfaff 19aa20a057 netlink-socket: Refill comment to fit within 79 columns. 
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>
2014-07-15 10:00:58 -07:00

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/*
* Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "netlink-socket.h"
#include <errno.h>
#include <inttypes.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include "coverage.h"
#include "dynamic-string.h"
#include "hash.h"
#include "hmap.h"
#include "netlink.h"
#include "netlink-protocol.h"
#include "ofpbuf.h"
#include "ovs-thread.h"
#include "poll-loop.h"
#include "seq.h"
#include "socket-util.h"
#include "util.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(netlink_socket);
COVERAGE_DEFINE(netlink_overflow);
COVERAGE_DEFINE(netlink_received);
COVERAGE_DEFINE(netlink_recv_jumbo);
COVERAGE_DEFINE(netlink_sent);
/* Linux header file confusion causes this to be undefined. */
#ifndef SOL_NETLINK
#define SOL_NETLINK 270
#endif
/* A single (bad) Netlink message can in theory dump out many, many log
* messages, so the burst size is set quite high here to avoid missing useful
* information. Also, at high logging levels we log *all* Netlink messages. */
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(60, 600);
static uint32_t nl_sock_allocate_seq(struct nl_sock *, unsigned int n);
static void log_nlmsg(const char *function, int error,
const void *message, size_t size, int protocol);
/* Netlink sockets. */
struct nl_sock {
int fd;
uint32_t next_seq;
uint32_t pid;
int protocol;
unsigned int rcvbuf; /* Receive buffer size (SO_RCVBUF). */
};
/* Compile-time limit on iovecs, so that we can allocate a maximum-size array
* of iovecs on the stack. */
#define MAX_IOVS 128
/* Maximum number of iovecs that may be passed to sendmsg, capped at a
* minimum of _XOPEN_IOV_MAX (16) and a maximum of MAX_IOVS.
*
* Initialized by nl_sock_create(). */
static int max_iovs;
static int nl_pool_alloc(int protocol, struct nl_sock **sockp);
static void nl_pool_release(struct nl_sock *);
/* Creates a new netlink socket for the given netlink 'protocol'
* (NETLINK_ROUTE, NETLINK_GENERIC, ...). Returns 0 and sets '*sockp' to the
* new socket if successful, otherwise returns a positive errno value. */
int
nl_sock_create(int protocol, struct nl_sock **sockp)
{
static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
struct nl_sock *sock;
struct sockaddr_nl local, remote;
socklen_t local_size;
int rcvbuf;
int retval = 0;
if (ovsthread_once_start(&once)) {
int save_errno = errno;
errno = 0;
max_iovs = sysconf(_SC_UIO_MAXIOV);
if (max_iovs < _XOPEN_IOV_MAX) {
if (max_iovs == -1 && errno) {
VLOG_WARN("sysconf(_SC_UIO_MAXIOV): %s", ovs_strerror(errno));
}
max_iovs = _XOPEN_IOV_MAX;
} else if (max_iovs > MAX_IOVS) {
max_iovs = MAX_IOVS;
}
errno = save_errno;
ovsthread_once_done(&once);
}
*sockp = NULL;
sock = xmalloc(sizeof *sock);
sock->fd = socket(AF_NETLINK, SOCK_RAW, protocol);
if (sock->fd < 0) {
VLOG_ERR("fcntl: %s", ovs_strerror(errno));
goto error;
}
sock->protocol = protocol;
sock->next_seq = 1;
rcvbuf = 1024 * 1024;
if (setsockopt(sock->fd, SOL_SOCKET, SO_RCVBUFFORCE,
&rcvbuf, sizeof rcvbuf)) {
/* Only root can use SO_RCVBUFFORCE. Everyone else gets EPERM.
* Warn only if the failure is therefore unexpected. */
if (errno != EPERM) {
VLOG_WARN_RL(&rl, "setting %d-byte socket receive buffer failed "
"(%s)", rcvbuf, ovs_strerror(errno));
}
}
retval = get_socket_rcvbuf(sock->fd);
if (retval < 0) {
retval = -retval;
goto error;
}
sock->rcvbuf = retval;
/* Connect to kernel (pid 0) as remote address. */
memset(&remote, 0, sizeof remote);
remote.nl_family = AF_NETLINK;
remote.nl_pid = 0;
if (connect(sock->fd, (struct sockaddr *) &remote, sizeof remote) < 0) {
VLOG_ERR("connect(0): %s", ovs_strerror(errno));
goto error;
}
/* Obtain pid assigned by kernel. */
local_size = sizeof local;
if (getsockname(sock->fd, (struct sockaddr *) &local, &local_size) < 0) {
VLOG_ERR("getsockname: %s", ovs_strerror(errno));
goto error;
}
if (local_size < sizeof local || local.nl_family != AF_NETLINK) {
VLOG_ERR("getsockname returned bad Netlink name");
retval = EINVAL;
goto error;
}
sock->pid = local.nl_pid;
*sockp = sock;
return 0;
error:
if (retval == 0) {
retval = errno;
if (retval == 0) {
retval = EINVAL;
}
}
if (sock->fd >= 0) {
close(sock->fd);
}
free(sock);
return retval;
}
/* Creates a new netlink socket for the same protocol as 'src'. Returns 0 and
* sets '*sockp' to the new socket if successful, otherwise returns a positive
* errno value. */
int
nl_sock_clone(const struct nl_sock *src, struct nl_sock **sockp)
{
return nl_sock_create(src->protocol, sockp);
}
/* Destroys netlink socket 'sock'. */
void
nl_sock_destroy(struct nl_sock *sock)
{
if (sock) {
close(sock->fd);
free(sock);
}
}
/* Tries to add 'sock' as a listener for 'multicast_group'. Returns 0 if
* successful, otherwise a positive errno value.
*
* A socket that is subscribed to a multicast group that receives asynchronous
* notifications must not be used for Netlink transactions or dumps, because
* transactions and dumps can cause notifications to be lost.
*
* Multicast group numbers are always positive.
*
* It is not an error to attempt to join a multicast group to which a socket
* already belongs. */
int
nl_sock_join_mcgroup(struct nl_sock *sock, unsigned int multicast_group)
{
if (setsockopt(sock->fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP,
&multicast_group, sizeof multicast_group) < 0) {
VLOG_WARN("could not join multicast group %u (%s)",
multicast_group, ovs_strerror(errno));
return errno;
}
return 0;
}
/* Tries to make 'sock' stop listening to 'multicast_group'. Returns 0 if
* successful, otherwise a positive errno value.
*
* Multicast group numbers are always positive.
*
* It is not an error to attempt to leave a multicast group to which a socket
* does not belong.
*
* On success, reading from 'sock' will still return any messages that were
* received on 'multicast_group' before the group was left. */
int
nl_sock_leave_mcgroup(struct nl_sock *sock, unsigned int multicast_group)
{
if (setsockopt(sock->fd, SOL_NETLINK, NETLINK_DROP_MEMBERSHIP,
&multicast_group, sizeof multicast_group) < 0) {
VLOG_WARN("could not leave multicast group %u (%s)",
multicast_group, ovs_strerror(errno));
return errno;
}
return 0;
}
static int
nl_sock_send__(struct nl_sock *sock, const struct ofpbuf *msg,
uint32_t nlmsg_seq, bool wait)
{
struct nlmsghdr *nlmsg = nl_msg_nlmsghdr(msg);
int error;
nlmsg->nlmsg_len = ofpbuf_size(msg);
nlmsg->nlmsg_seq = nlmsg_seq;
nlmsg->nlmsg_pid = sock->pid;
do {
int retval;
retval = send(sock->fd, ofpbuf_data(msg), ofpbuf_size(msg), wait ? 0 : MSG_DONTWAIT);
error = retval < 0 ? errno : 0;
} while (error == EINTR);
log_nlmsg(__func__, error, ofpbuf_data(msg), ofpbuf_size(msg), sock->protocol);
if (!error) {
COVERAGE_INC(netlink_sent);
}
return error;
}
/* Tries to send 'msg', which must contain a Netlink message, to the kernel on
* 'sock'. nlmsg_len in 'msg' will be finalized to match ofpbuf_size(msg), nlmsg_pid
* will be set to 'sock''s pid, and nlmsg_seq will be initialized to a fresh
* sequence number, before the message is sent.
*
* Returns 0 if successful, otherwise a positive errno value. If
* 'wait' is true, then the send will wait until buffer space is ready;
* otherwise, returns EAGAIN if the 'sock' send buffer is full. */
int
nl_sock_send(struct nl_sock *sock, const struct ofpbuf *msg, bool wait)
{
return nl_sock_send_seq(sock, msg, nl_sock_allocate_seq(sock, 1), wait);
}
/* Tries to send 'msg', which must contain a Netlink message, to the kernel on
* 'sock'. nlmsg_len in 'msg' will be finalized to match ofpbuf_size(msg), nlmsg_pid
* will be set to 'sock''s pid, and nlmsg_seq will be initialized to
* 'nlmsg_seq', before the message is sent.
*
* Returns 0 if successful, otherwise a positive errno value. If
* 'wait' is true, then the send will wait until buffer space is ready;
* otherwise, returns EAGAIN if the 'sock' send buffer is full.
*
* This function is suitable for sending a reply to a request that was received
* with sequence number 'nlmsg_seq'. Otherwise, use nl_sock_send() instead. */
int
nl_sock_send_seq(struct nl_sock *sock, const struct ofpbuf *msg,
uint32_t nlmsg_seq, bool wait)
{
return nl_sock_send__(sock, msg, nlmsg_seq, wait);
}
static int
nl_sock_recv__(struct nl_sock *sock, struct ofpbuf *buf, bool wait)
{
/* We can't accurately predict the size of the data to be received. The
* caller is supposed to have allocated enough space in 'buf' to handle the
* "typical" case. To handle exceptions, we make available enough space in
* 'tail' to allow Netlink messages to be up to 64 kB long (a reasonable
* figure since that's the maximum length of a Netlink attribute). */
struct nlmsghdr *nlmsghdr;
uint8_t tail[65536];
struct iovec iov[2];
struct msghdr msg;
ssize_t retval;
int error;
ovs_assert(buf->allocated >= sizeof *nlmsghdr);
ofpbuf_clear(buf);
iov[0].iov_base = ofpbuf_base(buf);
iov[0].iov_len = buf->allocated;
iov[1].iov_base = tail;
iov[1].iov_len = sizeof tail;
memset(&msg, 0, sizeof msg);
msg.msg_iov = iov;
msg.msg_iovlen = 2;
/* Receive a Netlink message from the kernel.
*
* This works around a kernel bug in which the kernel returns an error code
* as if it were the number of bytes read. It doesn't actually modify
* anything in the receive buffer in that case, so we can initialize the
* Netlink header with an impossible message length and then, upon success,
* check whether it changed. */
nlmsghdr = ofpbuf_base(buf);
do {
nlmsghdr->nlmsg_len = UINT32_MAX;
retval = recvmsg(sock->fd, &msg, wait ? 0 : MSG_DONTWAIT);
error = (retval < 0 ? errno
: retval == 0 ? ECONNRESET /* not possible? */
: nlmsghdr->nlmsg_len != UINT32_MAX ? 0
: retval);
} while (error == EINTR);
if (error) {
if (error == ENOBUFS) {
/* Socket receive buffer overflow dropped one or more messages that
* the kernel tried to send to us. */
COVERAGE_INC(netlink_overflow);
}
return error;
}
if (msg.msg_flags & MSG_TRUNC) {
VLOG_ERR_RL(&rl, "truncated message (longer than %"PRIuSIZE" bytes)",
sizeof tail);
return E2BIG;
}
if (retval < sizeof *nlmsghdr
|| nlmsghdr->nlmsg_len < sizeof *nlmsghdr
|| nlmsghdr->nlmsg_len > retval) {
VLOG_ERR_RL(&rl, "received invalid nlmsg (%"PRIuSIZE" bytes < %"PRIuSIZE")",
retval, sizeof *nlmsghdr);
return EPROTO;
}
ofpbuf_set_size(buf, MIN(retval, buf->allocated));
if (retval > buf->allocated) {
COVERAGE_INC(netlink_recv_jumbo);
ofpbuf_put(buf, tail, retval - buf->allocated);
}
log_nlmsg(__func__, 0, ofpbuf_data(buf), ofpbuf_size(buf), sock->protocol);
COVERAGE_INC(netlink_received);
return 0;
}
/* Tries to receive a Netlink message from the kernel on 'sock' into 'buf'. If
* 'wait' is true, waits for a message to be ready. Otherwise, fails with
* EAGAIN if the 'sock' receive buffer is empty.
*
* The caller must have initialized 'buf' with an allocation of at least
* NLMSG_HDRLEN bytes. For best performance, the caller should allocate enough
* space for a "typical" message.
*
* On success, returns 0 and replaces 'buf''s previous content by the received
* message. This function expands 'buf''s allocated memory, as necessary, to
* hold the actual size of the received message.
*
* On failure, returns a positive errno value and clears 'buf' to zero length.
* 'buf' retains its previous memory allocation.
*
* Regardless of success or failure, this function resets 'buf''s headroom to
* 0. */
int
nl_sock_recv(struct nl_sock *sock, struct ofpbuf *buf, bool wait)
{
return nl_sock_recv__(sock, buf, wait);
}
static void
nl_sock_record_errors__(struct nl_transaction **transactions, size_t n,
int error)
{
size_t i;
for (i = 0; i < n; i++) {
struct nl_transaction *txn = transactions[i];
txn->error = error;
if (txn->reply) {
ofpbuf_clear(txn->reply);
}
}
}
static int
nl_sock_transact_multiple__(struct nl_sock *sock,
struct nl_transaction **transactions, size_t n,
size_t *done)
{
uint64_t tmp_reply_stub[1024 / 8];
struct nl_transaction tmp_txn;
struct ofpbuf tmp_reply;
uint32_t base_seq;
struct iovec iovs[MAX_IOVS];
struct msghdr msg;
int error;
int i;
base_seq = nl_sock_allocate_seq(sock, n);
*done = 0;
for (i = 0; i < n; i++) {
struct nl_transaction *txn = transactions[i];
struct nlmsghdr *nlmsg = nl_msg_nlmsghdr(txn->request);
nlmsg->nlmsg_len = ofpbuf_size(txn->request);
nlmsg->nlmsg_seq = base_seq + i;
nlmsg->nlmsg_pid = sock->pid;
iovs[i].iov_base = ofpbuf_data(txn->request);
iovs[i].iov_len = ofpbuf_size(txn->request);
}
memset(&msg, 0, sizeof msg);
msg.msg_iov = iovs;
msg.msg_iovlen = n;
do {
error = sendmsg(sock->fd, &msg, 0) < 0 ? errno : 0;
} while (error == EINTR);
for (i = 0; i < n; i++) {
struct nl_transaction *txn = transactions[i];
log_nlmsg(__func__, error, ofpbuf_data(txn->request), ofpbuf_size(txn->request),
sock->protocol);
}
if (!error) {
COVERAGE_ADD(netlink_sent, n);
}
if (error) {
return error;
}
ofpbuf_use_stub(&tmp_reply, tmp_reply_stub, sizeof tmp_reply_stub);
tmp_txn.request = NULL;
tmp_txn.reply = &tmp_reply;
tmp_txn.error = 0;
while (n > 0) {
struct nl_transaction *buf_txn, *txn;
uint32_t seq;
/* Find a transaction whose buffer we can use for receiving a reply.
* If no such transaction is left, use tmp_txn. */
buf_txn = &tmp_txn;
for (i = 0; i < n; i++) {
if (transactions[i]->reply) {
buf_txn = transactions[i];
break;
}
}
/* Receive a reply. */
error = nl_sock_recv__(sock, buf_txn->reply, false);
if (error) {
if (error == EAGAIN) {
nl_sock_record_errors__(transactions, n, 0);
*done += n;
error = 0;
}
break;
}
/* Match the reply up with a transaction. */
seq = nl_msg_nlmsghdr(buf_txn->reply)->nlmsg_seq;
if (seq < base_seq || seq >= base_seq + n) {
VLOG_DBG_RL(&rl, "ignoring unexpected seq %#"PRIx32, seq);
continue;
}
i = seq - base_seq;
txn = transactions[i];
/* Fill in the results for 'txn'. */
if (nl_msg_nlmsgerr(buf_txn->reply, &txn->error)) {
if (txn->reply) {
ofpbuf_clear(txn->reply);
}
if (txn->error) {
VLOG_DBG_RL(&rl, "received NAK error=%d (%s)",
error, ovs_strerror(txn->error));
}
} else {
txn->error = 0;
if (txn->reply && txn != buf_txn) {
/* Swap buffers. */
struct ofpbuf *reply = buf_txn->reply;
buf_txn->reply = txn->reply;
txn->reply = reply;
}
}
/* Fill in the results for transactions before 'txn'. (We have to do
* this after the results for 'txn' itself because of the buffer swap
* above.) */
nl_sock_record_errors__(transactions, i, 0);
/* Advance. */
*done += i + 1;
transactions += i + 1;
n -= i + 1;
base_seq += i + 1;
}
ofpbuf_uninit(&tmp_reply);
return error;
}
/* Sends the 'request' member of the 'n' transactions in 'transactions' on
* 'sock', in order, and receives responses to all of them. Fills in the
* 'error' member of each transaction with 0 if it was successful, otherwise
* with a positive errno value. If 'reply' is nonnull, then it will be filled
* with the reply if the message receives a detailed reply. In other cases,
* i.e. where the request failed or had no reply beyond an indication of
* success, 'reply' will be cleared if it is nonnull.
*
* The caller is responsible for destroying each request and reply, and the
* transactions array itself.
*
* Before sending each message, this function will finalize nlmsg_len in each
* 'request' to match the ofpbuf's size, set nlmsg_pid to 'sock''s pid, and
* initialize nlmsg_seq.
*
* Bare Netlink is an unreliable transport protocol. This function layers
* reliable delivery and reply semantics on top of bare Netlink. See
* nl_sock_transact() for some caveats.
*/
void
nl_sock_transact_multiple(struct nl_sock *sock,
struct nl_transaction **transactions, size_t n)
{
int max_batch_count;
int error;
if (!n) {
return;
}
/* In theory, every request could have a 64 kB reply. But the default and
* maximum socket rcvbuf size with typical Dom0 memory sizes both tend to
* be a bit below 128 kB, so that would only allow a single message in a
* "batch". So we assume that replies average (at most) 4 kB, which allows
* a good deal of batching.
*
* In practice, most of the requests that we batch either have no reply at
* all or a brief reply. */
max_batch_count = MAX(sock->rcvbuf / 4096, 1);
max_batch_count = MIN(max_batch_count, max_iovs);
while (n > 0) {
size_t count, bytes;
size_t done;
/* Batch up to 'max_batch_count' transactions. But cap it at about a
* page of requests total because big skbuffs are expensive to
* allocate in the kernel. */
#if defined(PAGESIZE)
enum { MAX_BATCH_BYTES = MAX(1, PAGESIZE - 512) };
#else
enum { MAX_BATCH_BYTES = 4096 - 512 };
#endif
bytes = ofpbuf_size(transactions[0]->request);
for (count = 1; count < n && count < max_batch_count; count++) {
if (bytes + ofpbuf_size(transactions[count]->request) > MAX_BATCH_BYTES) {
break;
}
bytes += ofpbuf_size(transactions[count]->request);
}
error = nl_sock_transact_multiple__(sock, transactions, count, &done);
transactions += done;
n -= done;
if (error == ENOBUFS) {
VLOG_DBG_RL(&rl, "receive buffer overflow, resending request");
} else if (error) {
VLOG_ERR_RL(&rl, "transaction error (%s)", ovs_strerror(error));
nl_sock_record_errors__(transactions, n, error);
}
}
}
/* Sends 'request' to the kernel via 'sock' and waits for a response. If
* successful, returns 0. On failure, returns a positive errno value.
*
* If 'replyp' is nonnull, then on success '*replyp' is set to the kernel's
* reply, which the caller is responsible for freeing with ofpbuf_delete(), and
* on failure '*replyp' is set to NULL. If 'replyp' is null, then the kernel's
* reply, if any, is discarded.
*
* Before the message is sent, nlmsg_len in 'request' will be finalized to
* match ofpbuf_size(msg), nlmsg_pid will be set to 'sock''s pid, and nlmsg_seq will
* be initialized, NLM_F_ACK will be set in nlmsg_flags.
*
* The caller is responsible for destroying 'request'.
*
* Bare Netlink is an unreliable transport protocol. This function layers
* reliable delivery and reply semantics on top of bare Netlink.
*
* In Netlink, sending a request to the kernel is reliable enough, because the
* kernel will tell us if the message cannot be queued (and we will in that
* case put it on the transmit queue and wait until it can be delivered).
*
* Receiving the reply is the real problem: if the socket buffer is full when
* the kernel tries to send the reply, the reply will be dropped. However, the
* kernel sets a flag that a reply has been dropped. The next call to recv
* then returns ENOBUFS. We can then re-send the request.
*
* Caveats:
*
* 1. Netlink depends on sequence numbers to match up requests and
* replies. The sender of a request supplies a sequence number, and
* the reply echos back that sequence number.
*
* This is fine, but (1) some kernel netlink implementations are
* broken, in that they fail to echo sequence numbers and (2) this
* function will drop packets with non-matching sequence numbers, so
* that only a single request can be usefully transacted at a time.
*
* 2. Resending the request causes it to be re-executed, so the request
* needs to be idempotent.
*/
int
nl_sock_transact(struct nl_sock *sock, const struct ofpbuf *request,
struct ofpbuf **replyp)
{
struct nl_transaction *transactionp;
struct nl_transaction transaction;
transaction.request = CONST_CAST(struct ofpbuf *, request);
transaction.reply = replyp ? ofpbuf_new(1024) : NULL;
transactionp = &transaction;
nl_sock_transact_multiple(sock, &transactionp, 1);
if (replyp) {
if (transaction.error) {
ofpbuf_delete(transaction.reply);
*replyp = NULL;
} else {
*replyp = transaction.reply;
}
}
return transaction.error;
}
/* Drain all the messages currently in 'sock''s receive queue. */
int
nl_sock_drain(struct nl_sock *sock)
{
return drain_rcvbuf(sock->fd);
}
/* Starts a Netlink "dump" operation, by sending 'request' to the kernel on a
* Netlink socket created with the given 'protocol', and initializes 'dump' to
* reflect the state of the operation.
*
* 'request' must contain a Netlink message. Before sending the message,
* nlmsg_len will be finalized to match request->size, and nlmsg_pid will be
* set to the Netlink socket's pid. NLM_F_DUMP and NLM_F_ACK will be set in
* nlmsg_flags.
*
* The design of this Netlink socket library ensures that the dump is reliable.
*
* This function provides no status indication. nl_dump_done() provides an
* error status for the entire dump operation.
*
* The caller must eventually destroy 'request'.
*/
void
nl_dump_start(struct nl_dump *dump, int protocol, const struct ofpbuf *request)
{
int status = nl_pool_alloc(protocol, &dump->sock);
if (status) {
return;
}
nl_msg_nlmsghdr(request)->nlmsg_flags |= NLM_F_DUMP | NLM_F_ACK;
status = nl_sock_send__(dump->sock, request,
nl_sock_allocate_seq(dump->sock, 1), true);
atomic_init(&dump->status, status << 1);
dump->nl_seq = nl_msg_nlmsghdr(request)->nlmsg_seq;
dump->status_seq = seq_create();
ovs_mutex_init(&dump->mutex);
}
/* Attempts to retrieve another reply from 'dump' into 'buffer'. 'dump' must
* have been initialized with nl_dump_start(), and 'buffer' must have been
* initialized. 'buffer' should be at least NL_DUMP_BUFSIZE bytes long.
*
* If successful, returns true and points 'reply->data' and
* 'ofpbuf_size(reply)' to the message that was retrieved. The caller must not
* modify 'reply' (because it points within 'buffer', which will be used by
* future calls to this function).
*
* On failure, returns false and sets 'reply->data' to NULL and
* 'ofpbuf_size(reply)' to 0. Failure might indicate an actual error or merely
* the end of replies. An error status for the entire dump operation is
* provided when it is completed by calling nl_dump_done().
*
* Multiple threads may call this function, passing the same nl_dump, however
* each must provide independent buffers. This function may cache multiple
* replies in the buffer, and these will be processed before more replies are
* fetched. When this function returns false, other threads may continue to
* process replies in their buffers, but they will not fetch more replies.
*/
bool
nl_dump_next(struct nl_dump *dump, struct ofpbuf *reply, struct ofpbuf *buffer)
{
struct nlmsghdr *nlmsghdr;
int error = 0;
ofpbuf_set_data(reply, NULL);
ofpbuf_set_size(reply, 0);
/* If 'buffer' is empty, fetch another batch of nlmsgs. */
while (!ofpbuf_size(buffer)) {
unsigned int status;
int retval, seq;
seq = seq_read(dump->status_seq);
atomic_read(&dump->status, &status);
if (status) {
return false;
}
/* Take the mutex here to avoid an in-kernel race. If two threads try
* to read from a Netlink dump socket at once, then the socket error
* can be set to EINVAL, which will be encountered on the next recv on
* that socket, which could be anywhere due to the way that we pool
* Netlink sockets. Serializing the recv calls avoids the issue. */
ovs_mutex_lock(&dump->mutex);
retval = nl_sock_recv__(dump->sock, buffer, false);
ovs_mutex_unlock(&dump->mutex);
if (retval) {
ofpbuf_clear(buffer);
if (retval == EAGAIN) {
nl_sock_wait(dump->sock, POLLIN);
seq_wait(dump->status_seq, seq);
poll_block();
continue;
} else {
error = retval;
goto exit;
}
}
nlmsghdr = nl_msg_nlmsghdr(buffer);
if (dump->nl_seq != nlmsghdr->nlmsg_seq) {
VLOG_DBG_RL(&rl, "ignoring seq %#"PRIx32" != expected %#"PRIx32,
nlmsghdr->nlmsg_seq, dump->nl_seq);
ofpbuf_clear(buffer);
continue;
}
if (nl_msg_nlmsgerr(buffer, &retval) && retval) {
VLOG_INFO_RL(&rl, "netlink dump request error (%s)",
ovs_strerror(retval));
error = retval == EAGAIN ? EPROTO : retval;
ofpbuf_clear(buffer);
goto exit;
}
}
/* Fetch the next nlmsg in the current batch. */
nlmsghdr = nl_msg_next(buffer, reply);
if (!nlmsghdr) {
VLOG_WARN_RL(&rl, "netlink dump reply contains message fragment");
error = EPROTO;
} else if (nlmsghdr->nlmsg_type == NLMSG_DONE) {
error = EOF;
}
exit:
if (error == EOF) {
unsigned int old;
atomic_or(&dump->status, 1, &old);
seq_change(dump->status_seq);
} else if (error) {
atomic_store(&dump->status, error << 1);
seq_change(dump->status_seq);
}
return !error;
}
/* Completes Netlink dump operation 'dump', which must have been initialized
* with nl_dump_start(). Returns 0 if the dump operation was error-free,
* otherwise a positive errno value describing the problem. */
int
nl_dump_done(struct nl_dump *dump)
{
int status;
/* Drain any remaining messages that the client didn't read. Otherwise the
* kernel will continue to queue them up and waste buffer space.
*
* XXX We could just destroy and discard the socket in this case. */
atomic_read(&dump->status, &status);
if (!status) {
uint64_t tmp_reply_stub[NL_DUMP_BUFSIZE / 8];
struct ofpbuf reply, buf;
ofpbuf_use_stub(&buf, tmp_reply_stub, sizeof tmp_reply_stub);
while (nl_dump_next(dump, &reply, &buf)) {
/* Nothing to do. */
}
atomic_read(&dump->status, &status);
ovs_assert(status);
ofpbuf_uninit(&buf);
}
nl_pool_release(dump->sock);
seq_destroy(dump->status_seq);
ovs_mutex_destroy(&dump->mutex);
return status >> 1;
}
/* Causes poll_block() to wake up when any of the specified 'events' (which is
* a OR'd combination of POLLIN, POLLOUT, etc.) occur on 'sock'. */
void
nl_sock_wait(const struct nl_sock *sock, short int events)
{
poll_fd_wait(sock->fd, events);
}
/* Returns the underlying fd for 'sock', for use in "poll()"-like operations
* that can't use nl_sock_wait().
*
* It's a little tricky to use the returned fd correctly, because nl_sock does
* "copy on write" to allow a single nl_sock to be used for notifications,
* transactions, and dumps. If 'sock' is used only for notifications and
* transactions (and never for dump) then the usage is safe. */
int
nl_sock_fd(const struct nl_sock *sock)
{
return sock->fd;
}
/* Returns the PID associated with this socket. */
uint32_t
nl_sock_pid(const struct nl_sock *sock)
{
return sock->pid;
}
/* Miscellaneous. */
struct genl_family {
struct hmap_node hmap_node;
uint16_t id;
char *name;
};
static struct hmap genl_families = HMAP_INITIALIZER(&genl_families);
static const struct nl_policy family_policy[CTRL_ATTR_MAX + 1] = {
[CTRL_ATTR_FAMILY_ID] = {.type = NL_A_U16},
[CTRL_ATTR_MCAST_GROUPS] = {.type = NL_A_NESTED, .optional = true},
};
static struct genl_family *
find_genl_family_by_id(uint16_t id)
{
struct genl_family *family;
HMAP_FOR_EACH_IN_BUCKET (family, hmap_node, hash_int(id, 0),
&genl_families) {
if (family->id == id) {
return family;
}
}
return NULL;
}
static void
define_genl_family(uint16_t id, const char *name)
{
struct genl_family *family = find_genl_family_by_id(id);
if (family) {
if (!strcmp(family->name, name)) {
return;
}
free(family->name);
} else {
family = xmalloc(sizeof *family);
family->id = id;
hmap_insert(&genl_families, &family->hmap_node, hash_int(id, 0));
}
family->name = xstrdup(name);
}
static const char *
genl_family_to_name(uint16_t id)
{
if (id == GENL_ID_CTRL) {
return "control";
} else {
struct genl_family *family = find_genl_family_by_id(id);
return family ? family->name : "unknown";
}
}
static int
do_lookup_genl_family(const char *name, struct nlattr **attrs,
struct ofpbuf **replyp)
{
struct nl_sock *sock;
struct ofpbuf request, *reply;
int error;
*replyp = NULL;
error = nl_sock_create(NETLINK_GENERIC, &sock);
if (error) {
return error;
}
ofpbuf_init(&request, 0);
nl_msg_put_genlmsghdr(&request, 0, GENL_ID_CTRL, NLM_F_REQUEST,
CTRL_CMD_GETFAMILY, 1);
nl_msg_put_string(&request, CTRL_ATTR_FAMILY_NAME, name);
error = nl_sock_transact(sock, &request, &reply);
ofpbuf_uninit(&request);
if (error) {
nl_sock_destroy(sock);
return error;
}
if (!nl_policy_parse(reply, NLMSG_HDRLEN + GENL_HDRLEN,
family_policy, attrs, ARRAY_SIZE(family_policy))
|| nl_attr_get_u16(attrs[CTRL_ATTR_FAMILY_ID]) == 0) {
nl_sock_destroy(sock);
ofpbuf_delete(reply);
return EPROTO;
}
nl_sock_destroy(sock);
*replyp = reply;
return 0;
}
/* Finds the multicast group called 'group_name' in genl family 'family_name'.
* When successful, writes its result to 'multicast_group' and returns 0.
* Otherwise, clears 'multicast_group' and returns a positive error code.
*/
int
nl_lookup_genl_mcgroup(const char *family_name, const char *group_name,
unsigned int *multicast_group)
{
struct nlattr *family_attrs[ARRAY_SIZE(family_policy)];
const struct nlattr *mc;
struct ofpbuf *reply;
unsigned int left;
int error;
*multicast_group = 0;
error = do_lookup_genl_family(family_name, family_attrs, &reply);
if (error) {
return error;
}
if (!family_attrs[CTRL_ATTR_MCAST_GROUPS]) {
error = EPROTO;
goto exit;
}
NL_NESTED_FOR_EACH (mc, left, family_attrs[CTRL_ATTR_MCAST_GROUPS]) {
static const struct nl_policy mc_policy[] = {
[CTRL_ATTR_MCAST_GRP_ID] = {.type = NL_A_U32},
[CTRL_ATTR_MCAST_GRP_NAME] = {.type = NL_A_STRING},
};
struct nlattr *mc_attrs[ARRAY_SIZE(mc_policy)];
const char *mc_name;
if (!nl_parse_nested(mc, mc_policy, mc_attrs, ARRAY_SIZE(mc_policy))) {
error = EPROTO;
goto exit;
}
mc_name = nl_attr_get_string(mc_attrs[CTRL_ATTR_MCAST_GRP_NAME]);
if (!strcmp(group_name, mc_name)) {
*multicast_group =
nl_attr_get_u32(mc_attrs[CTRL_ATTR_MCAST_GRP_ID]);
error = 0;
goto exit;
}
}
error = EPROTO;
exit:
ofpbuf_delete(reply);
return error;
}
/* If '*number' is 0, translates the given Generic Netlink family 'name' to a
* number and stores it in '*number'. If successful, returns 0 and the caller
* may use '*number' as the family number. On failure, returns a positive
* errno value and '*number' caches the errno value. */
int
nl_lookup_genl_family(const char *name, int *number)
{
if (*number == 0) {
struct nlattr *attrs[ARRAY_SIZE(family_policy)];
struct ofpbuf *reply;
int error;
error = do_lookup_genl_family(name, attrs, &reply);
if (!error) {
*number = nl_attr_get_u16(attrs[CTRL_ATTR_FAMILY_ID]);
define_genl_family(*number, name);
} else {
*number = -error;
}
ofpbuf_delete(reply);
ovs_assert(*number != 0);
}
return *number > 0 ? 0 : -*number;
}
struct nl_pool {
struct nl_sock *socks[16];
int n;
};
static struct ovs_mutex pool_mutex = OVS_MUTEX_INITIALIZER;
static struct nl_pool pools[MAX_LINKS] OVS_GUARDED_BY(pool_mutex);
static int
nl_pool_alloc(int protocol, struct nl_sock **sockp)
{
struct nl_sock *sock = NULL;
struct nl_pool *pool;
ovs_assert(protocol >= 0 && protocol < ARRAY_SIZE(pools));
ovs_mutex_lock(&pool_mutex);
pool = &pools[protocol];
if (pool->n > 0) {
sock = pool->socks[--pool->n];
}
ovs_mutex_unlock(&pool_mutex);
if (sock) {
*sockp = sock;
return 0;
} else {
return nl_sock_create(protocol, sockp);
}
}
static void
nl_pool_release(struct nl_sock *sock)
{
if (sock) {
struct nl_pool *pool = &pools[sock->protocol];
ovs_mutex_lock(&pool_mutex);
if (pool->n < ARRAY_SIZE(pool->socks)) {
pool->socks[pool->n++] = sock;
sock = NULL;
}
ovs_mutex_unlock(&pool_mutex);
nl_sock_destroy(sock);
}
}
int
nl_transact(int protocol, const struct ofpbuf *request,
struct ofpbuf **replyp)
{
struct nl_sock *sock;
int error;
error = nl_pool_alloc(protocol, &sock);
if (error) {
*replyp = NULL;
return error;
}
error = nl_sock_transact(sock, request, replyp);
nl_pool_release(sock);
return error;
}
void
nl_transact_multiple(int protocol,
struct nl_transaction **transactions, size_t n)
{
struct nl_sock *sock;
int error;
error = nl_pool_alloc(protocol, &sock);
if (!error) {
nl_sock_transact_multiple(sock, transactions, n);
nl_pool_release(sock);
} else {
nl_sock_record_errors__(transactions, n, error);
}
}
static uint32_t
nl_sock_allocate_seq(struct nl_sock *sock, unsigned int n)
{
uint32_t seq = sock->next_seq;
sock->next_seq += n;
/* Make it impossible for the next request for sequence numbers to wrap
* around to 0. Start over with 1 to avoid ever using a sequence number of
* 0, because the kernel uses sequence number 0 for notifications. */
if (sock->next_seq >= UINT32_MAX / 2) {
sock->next_seq = 1;
}
return seq;
}
static void
nlmsghdr_to_string(const struct nlmsghdr *h, int protocol, struct ds *ds)
{
struct nlmsg_flag {
unsigned int bits;
const char *name;
};
static const struct nlmsg_flag flags[] = {
{ NLM_F_REQUEST, "REQUEST" },
{ NLM_F_MULTI, "MULTI" },
{ NLM_F_ACK, "ACK" },
{ NLM_F_ECHO, "ECHO" },
{ NLM_F_DUMP, "DUMP" },
{ NLM_F_ROOT, "ROOT" },
{ NLM_F_MATCH, "MATCH" },
{ NLM_F_ATOMIC, "ATOMIC" },
};
const struct nlmsg_flag *flag;
uint16_t flags_left;
ds_put_format(ds, "nl(len:%"PRIu32", type=%"PRIu16,
h->nlmsg_len, h->nlmsg_type);
if (h->nlmsg_type == NLMSG_NOOP) {
ds_put_cstr(ds, "(no-op)");
} else if (h->nlmsg_type == NLMSG_ERROR) {
ds_put_cstr(ds, "(error)");
} else if (h->nlmsg_type == NLMSG_DONE) {
ds_put_cstr(ds, "(done)");
} else if (h->nlmsg_type == NLMSG_OVERRUN) {
ds_put_cstr(ds, "(overrun)");
} else if (h->nlmsg_type < NLMSG_MIN_TYPE) {
ds_put_cstr(ds, "(reserved)");
} else if (protocol == NETLINK_GENERIC) {
ds_put_format(ds, "(%s)", genl_family_to_name(h->nlmsg_type));
} else {
ds_put_cstr(ds, "(family-defined)");
}
ds_put_format(ds, ", flags=%"PRIx16, h->nlmsg_flags);
flags_left = h->nlmsg_flags;
for (flag = flags; flag < &flags[ARRAY_SIZE(flags)]; flag++) {
if ((flags_left & flag->bits) == flag->bits) {
ds_put_format(ds, "[%s]", flag->name);
flags_left &= ~flag->bits;
}
}
if (flags_left) {
ds_put_format(ds, "[OTHER:%"PRIx16"]", flags_left);
}
ds_put_format(ds, ", seq=%"PRIx32", pid=%"PRIu32,
h->nlmsg_seq, h->nlmsg_pid);
}
static char *
nlmsg_to_string(const struct ofpbuf *buffer, int protocol)
{
struct ds ds = DS_EMPTY_INITIALIZER;
const struct nlmsghdr *h = ofpbuf_at(buffer, 0, NLMSG_HDRLEN);
if (h) {
nlmsghdr_to_string(h, protocol, &ds);
if (h->nlmsg_type == NLMSG_ERROR) {
const struct nlmsgerr *e;
e = ofpbuf_at(buffer, NLMSG_HDRLEN,
NLMSG_ALIGN(sizeof(struct nlmsgerr)));
if (e) {
ds_put_format(&ds, " error(%d", e->error);
if (e->error < 0) {
ds_put_format(&ds, "(%s)", ovs_strerror(-e->error));
}
ds_put_cstr(&ds, ", in-reply-to(");
nlmsghdr_to_string(&e->msg, protocol, &ds);
ds_put_cstr(&ds, "))");
} else {
ds_put_cstr(&ds, " error(truncated)");
}
} else if (h->nlmsg_type == NLMSG_DONE) {
int *error = ofpbuf_at(buffer, NLMSG_HDRLEN, sizeof *error);
if (error) {
ds_put_format(&ds, " done(%d", *error);
if (*error < 0) {
ds_put_format(&ds, "(%s)", ovs_strerror(-*error));
}
ds_put_cstr(&ds, ")");
} else {
ds_put_cstr(&ds, " done(truncated)");
}
} else if (protocol == NETLINK_GENERIC) {
struct genlmsghdr *genl = nl_msg_genlmsghdr(buffer);
if (genl) {
ds_put_format(&ds, ",genl(cmd=%"PRIu8",version=%"PRIu8")",
genl->cmd, genl->version);
}
}
} else {
ds_put_cstr(&ds, "nl(truncated)");
}
return ds.string;
}
static void
log_nlmsg(const char *function, int error,
const void *message, size_t size, int protocol)
{
struct ofpbuf buffer;
char *nlmsg;
if (!VLOG_IS_DBG_ENABLED()) {
return;
}
ofpbuf_use_const(&buffer, message, size);
nlmsg = nlmsg_to_string(&buffer, protocol);
VLOG_DBG_RL(&rl, "%s (%s): %s", function, ovs_strerror(error), nlmsg);
free(nlmsg);
}
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