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netlink-socket: Make caller provide message receive buffers.

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Typically an nl_sock client can stack-allocate the buffer for receiving
a Netlink message, which provides a performance boost.

Signed-off-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Ben Pfaff
2012-04-09 15:35:29 -07:00
parent 8843668ae5
commit 72d32ac0b3
6 changed files with 210 additions and 172 deletions
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264
lib/netlink-socket.c
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@@ -300,32 +300,26 @@ STRESS_OPTION(
5, 1, -1, 100);
static int
nl_sock_recv__(struct nl_sock *sock, struct ofpbuf **bufp, bool wait)
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. Most
* received data will fit in a 2 kB buffer, so we allocate that much space.
* In case the data is actually bigger than that, we make available enough
* additional space to allow Netlink messages to be up to 64 kB long (a
* reasonable figure since that's the maximum length of a Netlink
* attribute). */
enum { MAX_SIZE = 65536 };
enum { HEAD_SIZE = 2048 };
enum { TAIL_SIZE = MAX_SIZE - HEAD_SIZE };
/* 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[TAIL_SIZE];
uint8_t tail[65536];
struct iovec iov[2];
struct ofpbuf *buf;
struct msghdr msg;
ssize_t retval;
*bufp = NULL;
assert(buf->allocated >= sizeof *nlmsghdr);
ofpbuf_clear(buf);
buf = ofpbuf_new(HEAD_SIZE);
iov[0].iov_base = buf->data;
iov[0].iov_len = HEAD_SIZE;
iov[0].iov_base = buf->base;
iov[0].iov_len = buf->allocated;
iov[1].iov_base = tail;
iov[1].iov_len = TAIL_SIZE;
iov[1].iov_len = sizeof tail;
memset(&msg, 0, sizeof msg);
msg.msg_iov = iov;
@@ -342,77 +336,65 @@ nl_sock_recv__(struct nl_sock *sock, struct ofpbuf **bufp, bool wait)
* the kernel tried to send to us. */
COVERAGE_INC(netlink_overflow);
}
ofpbuf_delete(buf);
return error;
}
if (msg.msg_flags & MSG_TRUNC) {
VLOG_ERR_RL(&rl, "truncated message (longer than %d bytes)", MAX_SIZE);
ofpbuf_delete(buf);
VLOG_ERR_RL(&rl, "truncated message (longer than %zu bytes)",
sizeof tail);
return E2BIG;
}
ofpbuf_put_uninit(buf, MIN(retval, HEAD_SIZE));
if (retval > HEAD_SIZE) {
COVERAGE_INC(netlink_recv_jumbo);
ofpbuf_put(buf, tail, retval - HEAD_SIZE);
}
nlmsghdr = buf->data;
if (retval < sizeof *nlmsghdr
|| nlmsghdr->nlmsg_len < sizeof *nlmsghdr
|| nlmsghdr->nlmsg_len > retval) {
VLOG_ERR_RL(&rl, "received invalid nlmsg (%zd bytes < %d)",
retval, NLMSG_HDRLEN);
ofpbuf_delete(buf);
VLOG_ERR_RL(&rl, "received invalid nlmsg (%zd bytes < %zu)",
retval, sizeof *nlmsghdr);
return EPROTO;
}
if (STRESS(netlink_overflow)) {
ofpbuf_delete(buf);
return ENOBUFS;
}
*bufp = buf;
buf->size = MIN(retval, buf->allocated);
if (retval > buf->allocated) {
COVERAGE_INC(netlink_recv_jumbo);
ofpbuf_put(buf, tail, retval - buf->allocated);
}
log_nlmsg(__func__, 0, buf->data, buf->size, sock->protocol);
COVERAGE_INC(netlink_received);
return 0;
}
/* Tries to receive a netlink message from the kernel on 'sock'. If
* successful, stores the received message into '*bufp' and returns 0. The
* caller is responsible for destroying the message with ofpbuf_delete(). On
* failure, returns a positive errno value and stores a null pointer into
* '*bufp'.
/* 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.
*
* If 'wait' is true, nl_sock_recv waits for a message to be ready; otherwise,
* returns 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 **bufp, bool wait)
nl_sock_recv(struct nl_sock *sock, struct ofpbuf *buf, bool wait)
{
int error = nl_sock_cow__(sock);
if (error) {
return error;
}
return nl_sock_recv__(sock, bufp, wait);
}
static int
find_nl_transaction_by_seq(struct nl_transaction **transactions, size_t n,
uint32_t seq)
{
int i;
for (i = 0; i < n; i++) {
struct nl_transaction *t = transactions[i];
if (seq == nl_msg_nlmsghdr(t->request)->nlmsg_seq) {
return i;
}
}
return -1;
return nl_sock_recv__(sock, buf, wait);
}
static void
@@ -422,8 +404,12 @@ nl_sock_record_errors__(struct nl_transaction **transactions, size_t n,
size_t i;
for (i = 0; i < n; i++) {
transactions[i]->error = error;
transactions[i]->reply = NULL;
struct nl_transaction *txn = transactions[i];
txn->error = error;
if (txn->reply) {
ofpbuf_clear(txn->reply);
}
}
}
@@ -432,21 +418,28 @@ 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 ofpbuf *request = transactions[i]->request;
struct nlmsghdr *nlmsg = nl_msg_nlmsghdr(request);
struct nl_transaction *txn = transactions[i];
struct nlmsghdr *nlmsg = nl_msg_nlmsghdr(txn->request);
nlmsg->nlmsg_len = request->size;
nlmsg->nlmsg_len = txn->request->size;
nlmsg->nlmsg_seq = base_seq + i;
nlmsg->nlmsg_pid = sock->pid;
iovs[i].iov_base = request->data;
iovs[i].iov_len = request->size;
iovs[i].iov_base = txn->request->data;
iovs[i].iov_len = txn->request->size;
}
memset(&msg, 0, sizeof msg);
@@ -457,9 +450,9 @@ nl_sock_transact_multiple__(struct nl_sock *sock,
} while (error == EINTR);
for (i = 0; i < n; i++) {
struct ofpbuf *request = transactions[i]->request;
struct nl_transaction *txn = transactions[i];
log_nlmsg(__func__, error, request->data, request->size,
log_nlmsg(__func__, error, txn->request->data, txn->request->size,
sock->protocol);
}
if (!error) {
@@ -470,62 +463,93 @@ nl_sock_transact_multiple__(struct nl_sock *sock,
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 ofpbuf *reply;
struct nl_transaction *buf_txn, *txn;
uint32_t seq;
error = nl_sock_recv__(sock, &reply, false);
if (error == EAGAIN) {
nl_sock_record_errors__(transactions, n, 0);
*done += n;
return 0;
} else if (error) {
return error;
/* 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;
}
}
i = find_nl_transaction_by_seq(transactions, n,
nl_msg_nlmsghdr(reply)->nlmsg_seq);
if (i < 0) {
VLOG_DBG_RL(&rl, "ignoring unexpected seq %#"PRIx32,
nl_msg_nlmsghdr(reply)->nlmsg_seq);
ofpbuf_delete(reply);
/* 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];
nl_sock_record_errors__(transactions, i, 0);
if (nl_msg_nlmsgerr(reply, &error)) {
transactions[i]->reply = NULL;
transactions[i]->error = error;
if (error) {
VLOG_DBG_RL(&rl, "received NAK error=%d (%s)",
error, strerror(error));
/* 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, strerror(txn->error));
}
ofpbuf_delete(reply);
} else {
transactions[i]->reply = reply;
transactions[i]->error = 0;
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 0;
return error;
}
/* Sends the 'request' member of the 'n' transactions in 'transactions' to the
* kernel, in order, and waits for responses to all of them. Fills in the
/* 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. 'reply' will be NULL on error or if the
* transaction was successful but had no reply beyond an indication of success.
* For a successful transaction that did have a more detailed reply, 'reply'
* will be set to the reply message.
* 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, and set nlmsg_pid to 'sock''s pid.
* '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
@@ -640,13 +664,20 @@ nl_sock_transact(struct nl_sock *sock, const struct ofpbuf *request,
struct nl_transaction transaction;
transaction.request = (struct ofpbuf *) request;
transaction.reply = replyp ? ofpbuf_new(1024) : NULL;
transactionp = &transaction;
nl_sock_transact_multiple(sock, &transactionp, 1);
if (replyp) {
*replyp = transaction.reply;
} else {
ofpbuf_delete(transaction.reply);
if (transaction.error) {
ofpbuf_delete(transaction.reply);
*replyp = NULL;
} else {
*replyp = transaction.reply;
}
}
return transaction.error;
}
@@ -724,7 +755,7 @@ void
nl_dump_start(struct nl_dump *dump,
struct nl_sock *sock, const struct ofpbuf *request)
{
dump->buffer = NULL;
ofpbuf_init(&dump->buffer, 4096);
if (sock->dump) {
/* 'sock' already has an ongoing dump. Clone the socket because
* Netlink only allows one dump at a time. */
@@ -745,26 +776,24 @@ nl_dump_start(struct nl_dump *dump,
/* Helper function for nl_dump_next(). */
static int
nl_dump_recv(struct nl_dump *dump, struct ofpbuf **bufferp)
nl_dump_recv(struct nl_dump *dump)
{
struct nlmsghdr *nlmsghdr;
struct ofpbuf *buffer;
int retval;
retval = nl_sock_recv__(dump->sock, bufferp, true);
retval = nl_sock_recv__(dump->sock, &dump->buffer, true);
if (retval) {
return retval == EINTR ? EAGAIN : retval;
}
buffer = *bufferp;
nlmsghdr = nl_msg_nlmsghdr(buffer);
nlmsghdr = nl_msg_nlmsghdr(&dump->buffer);
if (dump->seq != nlmsghdr->nlmsg_seq) {
VLOG_DBG_RL(&rl, "ignoring seq %#"PRIx32" != expected %#"PRIx32,
nlmsghdr->nlmsg_seq, dump->seq);
return EAGAIN;
}
if (nl_msg_nlmsgerr(buffer, &retval)) {
if (nl_msg_nlmsgerr(&dump->buffer, &retval)) {
VLOG_INFO_RL(&rl, "netlink dump request error (%s)",
strerror(retval));
return retval && retval != EAGAIN ? retval : EPROTO;
@@ -796,15 +825,10 @@ nl_dump_next(struct nl_dump *dump, struct ofpbuf *reply)
return false;
}
if (dump->buffer && !dump->buffer->size) {
ofpbuf_delete(dump->buffer);
dump->buffer = NULL;
}
while (!dump->buffer) {
int retval = nl_dump_recv(dump, &dump->buffer);
while (!dump->buffer.size) {
int retval = nl_dump_recv(dump);
if (retval) {
ofpbuf_delete(dump->buffer);
dump->buffer = NULL;
ofpbuf_clear(&dump->buffer);
if (retval != EAGAIN) {
dump->status = retval;
return false;
@@ -812,7 +836,7 @@ nl_dump_next(struct nl_dump *dump, struct ofpbuf *reply)
}
}
nlmsghdr = nl_msg_next(dump->buffer, reply);
nlmsghdr = nl_msg_next(&dump->buffer, reply);
if (!nlmsghdr) {
VLOG_WARN_RL(&rl, "netlink dump reply contains message fragment");
dump->status = EPROTO;
@@ -847,7 +871,7 @@ nl_dump_done(struct nl_dump *dump)
nl_sock_destroy(dump->sock);
}
}
ofpbuf_delete(dump->buffer);
ofpbuf_uninit(&dump->buffer);
return dump->status == EOF ? 0 : dump->status;
}
@@ -1191,5 +1215,3 @@ log_nlmsg(const char *function, int error,
VLOG_DBG_RL(&rl, "%s (%s): %s", function, strerror(error), nlmsg);
free(nlmsg);
}