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net_serv.cc
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/* Copyright (c) 2000, 2024, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.
This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation. The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.
Without limiting anything contained in the foregoing, this file,
which is part of C Driver for MySQL (Connector/C), is also subject to the
Universal FOSS Exception, version 1.0, a copy of which can be found at
http://oss.oracle.com/licenses/universal-foss-exception.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License, version 2.0, for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
/**
@file
This file is the net layer API for the MySQL client/server protocol.
Write and read of logical packets to/from socket.
Writes are cached into net_buffer_length big packets.
Read packets are reallocated dynamically when reading big packets.
Each logical packet has the following pre-info:
3 byte length & 1 byte package-number.
*/
#include <string.h>
#include <sys/types.h>
#include <algorithm>
#include <mysql/components/services/log_builtins.h>
#include <mysql/thread_pool_priv.h>
#include "../sql/current_thd.h"
#include "../sql/sql_class.h"
#include "../sql/sql_thd_internal_api.h"
#include "my_byteorder.h"
#include "my_compiler.h"
#include "my_dbug.h"
#include "my_io.h"
#include "my_macros.h"
#include "my_sys.h"
#include "mysql.h"
#include "mysql/service_mysql_alloc.h"
#include "mysql_async.h"
#include "mysql_com.h"
#include "mysqld_error.h"
#include "violite.h"
using std::max;
using std::min;
#ifdef MYSQL_SERVER
#include "sql/psi_memory_key.h"
#else
#define key_memory_NET_buff 0
#define key_memory_NET_compress_packet 0
#endif
/*
The following handles the differences when this is linked between the
client and the server.
This gives an error if a too big packet is found.
The server can change this, but because the client can't normally do this
the client should have a bigger max_allowed_packet.
*/
#ifdef MYSQL_SERVER
/*
The following variables/functions should really not be declared
extern, but as it's hard to include sql_class.h here, we have to
live with this for a while.
*/
extern void thd_increment_bytes_sent(size_t length);
extern void thd_increment_bytes_received(size_t length);
/* Additional instrumentation hooks for the server */
#include "mysql_com_server.h"
#endif
static bool net_write_buff(NET *, const uchar *, size_t);
static uchar *compress_packet(NET *net, const uchar *packet, size_t *length);
NET_EXTENSION *net_extension_init() {
NET_EXTENSION *ext = static_cast<NET_EXTENSION *>(my_malloc(
PSI_NOT_INSTRUMENTED, sizeof(NET_EXTENSION), MYF(MY_WME | MY_ZEROFILL)));
ext->net_async_context = static_cast<NET_ASYNC *>(my_malloc(
PSI_NOT_INSTRUMENTED, sizeof(NET_ASYNC), MYF(MY_WME | MY_ZEROFILL)));
ext->compress_ctx.algorithm = enum_compression_algorithm::MYSQL_UNCOMPRESSED;
return ext;
}
void net_extension_free(NET *net) {
NET_EXTENSION *ext = NET_EXTENSION_PTR(net);
if (ext) {
#ifndef MYSQL_SERVER
if (ext->net_async_context) {
my_free(ext->net_async_context);
ext->net_async_context = nullptr;
}
mysql_compress_context_deinit(&ext->compress_ctx);
my_free(ext);
net->extension = nullptr;
#endif
}
}
/**
Returns the appropriate compression_context based on caller.
If the caller is server then fetch is from the server extension
structure.
@param[in] net NET structure
@returns mysql_compress_context structure pointer
*/
static mysql_compress_context *compress_context(NET *net) {
mysql_compress_context *mysql_compress_ctx = nullptr;
#ifdef MYSQL_SERVER
NET_SERVER *server_extension = static_cast<NET_SERVER *>(net->extension);
if (server_extension != nullptr) {
mysql_compress_ctx = &server_extension->compress_ctx;
}
#else
NET_EXTENSION *ext = NET_EXTENSION_PTR(net);
if (ext != nullptr) mysql_compress_ctx = &ext->compress_ctx;
#endif
return mysql_compress_ctx;
}
/** Init with packet info. */
bool my_net_init(NET *net, Vio *vio) {
DBUG_TRACE;
net->vio = vio;
my_net_local_init(net); /* Set some limits */
if (!(net->buff = (uchar *)my_malloc(
key_memory_NET_buff,
(size_t)net->max_packet + NET_HEADER_SIZE + COMP_HEADER_SIZE,
MYF(MY_WME))))
return true;
net->buff_end = net->buff + net->max_packet;
net->error = NET_ERROR_UNSET;
net->return_status = nullptr;
net->pkt_nr = net->compress_pkt_nr = 0;
net->write_pos = net->read_pos = net->buff;
net->last_error[0] = 0;
net->compress = false;
net->reading_or_writing = 0;
net->where_b = net->remain_in_buf = 0;
net->last_errno = 0;
#ifdef MYSQL_SERVER
net->extension = nullptr;
#else
NET_EXTENSION *ext = net_extension_init();
ext->net_async_context->cur_pos = net->buff + net->where_b;
ext->net_async_context->read_rows_is_first_read = true;
ext->net_async_context->async_operation = NET_ASYNC_OP_IDLE;
ext->net_async_context->async_send_command_status =
NET_ASYNC_SEND_COMMAND_IDLE;
ext->net_async_context->async_read_query_result_status =
NET_ASYNC_READ_QUERY_RESULT_IDLE;
ext->net_async_context->async_packet_read_state = NET_ASYNC_PACKET_READ_IDLE;
ext->compress_ctx.algorithm = enum_compression_algorithm::MYSQL_UNCOMPRESSED;
net->extension = ext;
#endif
if (vio) {
/* For perl DBI/DBD. */
net->fd = vio_fd(vio);
vio_fastsend(vio);
}
return false;
}
void net_end(NET *net) {
DBUG_TRACE;
#ifdef MYSQL_SERVER
NET_SERVER *server_extension = static_cast<NET_SERVER *>(net->extension);
if (server_extension != nullptr)
mysql_compress_context_deinit(&server_extension->compress_ctx);
#else
net_extension_free(net);
#endif
my_free(net->buff);
net->buff = nullptr;
}
void net_claim_memory_ownership(NET *net, bool claim) {
my_claim(net->buff, claim);
}
/** Realloc the packet buffer. */
bool net_realloc(NET *net, size_t length) {
uchar *buff;
size_t pkt_length;
DBUG_TRACE;
DBUG_PRINT("enter", ("length: %lu", (ulong)length));
if (length >= net->max_packet_size) {
DBUG_PRINT("error",
("Packet too large. Max size: %lu", net->max_packet_size));
/* Error, but no need to stop using the socket. */
net->error = NET_ERROR_SOCKET_RECOVERABLE;
net->last_errno = ER_NET_PACKET_TOO_LARGE;
#ifdef MYSQL_SERVER
my_error(ER_NET_PACKET_TOO_LARGE, MYF(0));
#endif
return true;
}
pkt_length = (length + IO_SIZE - 1) & ~(IO_SIZE - 1);
/*
We must allocate some extra bytes for the end 0 and to be able to
read big compressed blocks in
net_read_packet() may actually read 4 bytes depending on build flags and
platform.
*/
if (!(buff = (uchar *)my_realloc(
key_memory_NET_buff, (char *)net->buff,
pkt_length + NET_HEADER_SIZE + COMP_HEADER_SIZE, MYF(MY_WME)))) {
/* Error, but no need to stop using the socket. */
net->error = NET_ERROR_SOCKET_RECOVERABLE;
net->last_errno = ER_OUT_OF_RESOURCES;
/* In the server the error is reported by MY_WME flag. */
return true;
}
#ifdef MYSQL_SERVER
net->buff = net->write_pos = buff;
#else
const size_t cur_pos_offset = NET_ASYNC_DATA(net)->cur_pos - net->buff;
net->buff = net->write_pos = buff;
NET_ASYNC_DATA(net)->cur_pos = net->buff + cur_pos_offset;
#endif
net->buff_end = buff + (net->max_packet = (ulong)pkt_length);
return false;
}
/**
Clear (reinitialize) the NET structure for a new command.
@remark Performs debug checking of the socket buffer to
ensure that the protocol sequence is correct.
@param net NET handler
@param check_buffer Whether to check the socket buffer.
*/
void net_clear(NET *net, bool check_buffer [[maybe_unused]]) {
DBUG_TRACE;
DBUG_EXECUTE_IF("simulate_bad_field_length_1", {
net->pkt_nr = net->compress_pkt_nr = 0;
net->write_pos = net->buff;
return;
});
DBUG_EXECUTE_IF("simulate_bad_field_length_2", {
net->pkt_nr = net->compress_pkt_nr = 0;
net->write_pos = net->buff;
return;
});
/* Ready for new command */
net->pkt_nr = net->compress_pkt_nr = 0;
net->write_pos = net->buff;
}
/** Flush write_buffer if not empty. */
bool net_flush(NET *net) {
bool error = false;
DBUG_TRACE;
if (net->buff != net->write_pos) {
error =
net_write_packet(net, net->buff, (size_t)(net->write_pos - net->buff));
net->write_pos = net->buff;
}
/* Sync packet number if using compression */
if (net->compress) net->pkt_nr = net->compress_pkt_nr;
return error;
}
/**
Whether a I/O operation should be retried later.
@param net NET handler.
@param retry_count Maximum number of interrupted operations.
@retval true Operation should be retried.
@retval false Operation should not be retried. Fatal error.
*/
static bool net_should_retry(NET *net, uint *retry_count [[maybe_unused]]) {
bool retry;
#ifndef MYSQL_SERVER
/*
In the client library, interrupted I/O operations are always retried.
Otherwise, it's either a timeout or an unrecoverable error.
*/
retry = vio_should_retry(net->vio);
#else
/*
In the server, interrupted I/O operations are retried up to a limit.
In this scenario, pthread_kill can be used to wake up
(interrupt) threads waiting for I/O.
*/
retry = vio_should_retry(net->vio) && ((*retry_count)++ < net->retry_count);
#endif
return retry;
}
/* clang-format off */
/**
@page page_protocol_basic_packets MySQL Packets
If a MySQL client or server wants to send data, it:
- Splits the data into packets of size 2<sup>24</sup> bytes
- Prepends to each chunk a packet header
@section sect_protocol_basic_packets_packet Protocol::Packet
Data between client and server is exchanged in packets of max 16MByte size.
<table>
<caption>Payload</caption>
<tr><th>Type</th><th>Name</th><th>Description</th></tr>
<tr><td>@ref a_protocol_type_int1 "int<3>"</td>
<td>payload_length</td>
<td>Length of the payload. The number of bytes in the packet beyond
the initial 4 bytes that make up the packet header.</td></tr>
<tr><td>@ref a_protocol_type_int1 "int<1>"</td>
<td>sequence_id</td>
<td>@ref sect_protocol_basic_packets_sequence_id</td></tr>
<tr><td>@ref sect_protocol_basic_dt_string_var "string<var>"</td>
<td>payload</td>
<td>payload of the packet</td></tr>
</table>
Example:
@todo: Reference COM_QUIT
A COM_QUIT looks like this:
<table><tr>
<td>
~~~~~~~~~~~~~~~~~~~~~
01 00 00 00 01
~~~~~~~~~~~~~~~~~~~~~
</td><td>
- length: 1
- sequence_id: x00
- payload: 0x01
</td></tr></table>
@sa my_net_write(), net_write_command(), net_write_buff(), my_net_read(),
net_send_ok()
@section sect_protocol_basic_packets_sending_mt_16mb Sending More Than 16Mb
If the payload is larger than or equal to 2<sup>24</sup>-1 bytes the length
is set to 2<sup>24</sup>-1 (`ff ff ff`) and a additional packets are sent
with the rest of the payload until the payload of a packet is less
than 2<sup>24</sup>-1 bytes.
Sending a payload of 16 777 215 (2<sup>24</sup>-1) bytes looks like:
~~~~~~~~~~~~~~~~
ff ff ff 00 ...
00 00 00 01
~~~~~~~~~~~~~~~~
@section sect_protocol_basic_packets_sequence_id Sequence ID
The sequence-id is incremented with each packet and may wrap around.
It starts at 0 and is reset to 0 when a new command begins in the
@ref page_protocol_command_phase.
@section sect_protocol_basic_packets_describing_packets Describing Packets
In this document we describe each packet by first defining its payload and
provide an example showing each packet that is sent, including its packet
header:
<pre>
<packetname>
<description>
direction: client -> server
response: <response>
payload:
<type> <description>
</pre>
Example:
~~~~~~~~~~~~~~~~~~~~~
01 00 00 00 01
~~~~~~~~~~~~~~~~~~~~~
@note Some packets have optional fields or a different layout depending on
the @ref group_cs_capabilities_flags.
If a field has a fixed value, its description shows it as a hex value in
brackets like this: `[00]`
*/
/* clang-format on */
/*****************************************************************************
** Write something to server/client buffer
*****************************************************************************/
/**
Write a logical packet with packet header.
Format: Packet length (3 bytes), packet number (1 byte)
When compression is used, a 3 byte compression length is added.
@note If compression is used, the original packet is modified!
*/
bool my_net_write(NET *net, const uchar *packet, size_t len) {
uchar buff[NET_HEADER_SIZE];
DBUG_DUMP("net write", packet, len);
if (unlikely(!net->vio)) /* nowhere to write */
return false;
DBUG_EXECUTE_IF("simulate_net_write_failure", {
my_error(ER_NET_ERROR_ON_WRITE, MYF(0));
return 1;
};);
/* turn off non blocking operations */
if (!vio_is_blocking(net->vio)) vio_set_blocking_flag(net->vio, true);
/*
Big packets are handled by splitting them in packets of MAX_PACKET_LENGTH
length. The last packet is always a packet that is < MAX_PACKET_LENGTH.
(The last packet may even have a length of 0)
*/
while (len >= MAX_PACKET_LENGTH) {
const ulong z_size = MAX_PACKET_LENGTH;
int3store(buff, z_size);
buff[3] = (uchar)net->pkt_nr++;
if (net_write_buff(net, buff, NET_HEADER_SIZE) ||
net_write_buff(net, packet, z_size)) {
return true;
}
packet += z_size;
len -= z_size;
}
/* Write last packet */
int3store(buff, static_cast<uint>(len));
buff[3] = (uchar)net->pkt_nr++;
if (net_write_buff(net, buff, NET_HEADER_SIZE)) {
return true;
}
#ifdef DEBUG_DATA_PACKETS
DBUG_DUMP("packet_header", buff, NET_HEADER_SIZE);
#endif
return net_write_buff(net, packet, len);
}
static void reset_packet_write_state(NET *net) {
DBUG_TRACE;
NET_ASYNC *net_async = NET_ASYNC_DATA(net);
if (net_async->async_write_vector) {
if (net_async->async_write_vector != net_async->inline_async_write_vector) {
my_free(net_async->async_write_vector);
}
net_async->async_write_vector = nullptr;
}
if (net_async->async_write_headers) {
if (net_async->async_write_headers !=
net_async->inline_async_write_header) {
my_free(net_async->async_write_headers);
}
net_async->async_write_headers = nullptr;
}
net_async->async_write_vector_size = 0;
net_async->async_write_vector_current = 0;
if (net_async->compressed_write_buffers) {
/*
There are two entries per packet, one for header and one for payload.
We only need to free payloads as headers have their own buffer. If the
last packet was size 0, the vector size will be 1 lower and due to int
truncation for odd numbers will be correctly accounted for.
*/
for (size_t i = 0; i < net_async->compressed_buffers_size; ++i) {
my_free(net_async->compressed_write_buffers[i]);
}
my_free(net_async->compressed_write_buffers);
net_async->compressed_write_buffers = nullptr;
net_async->compressed_buffers_size = 0;
}
}
/*
Construct the proper buffers for our nonblocking write. What we do
here is we make an iovector for the entire write (header, command,
and payload). We then continually call writev on this vector,
consuming parts from it as bytes are successfully written. Headers
for the message are all stored inside one buffer, separate from the
payload; this lets us avoid copying the entire query just to insert
the headers every 2**24 bytes.
The most common case is the query fits in a packet. In that case,
we don't construct the iovector dynamically, instead using one we
pre-allocated inside the net structure. This avoids allocations in
the common path, but requires special casing with our iovec and
header buffer.
*/
static int begin_packet_write_state(NET *net, uchar command,
const uchar *packet, size_t packet_len,
const uchar *optional_prefix,
size_t prefix_len) {
DBUG_TRACE;
size_t header_len = NET_HEADER_SIZE;
if (net->compress) {
header_len += NET_HEADER_SIZE + COMP_HEADER_SIZE;
}
NET_ASYNC *net_async = NET_ASYNC_DATA(net);
size_t total_len = packet_len + prefix_len;
const bool include_command = (command < COM_END);
if (include_command) {
++total_len;
}
const size_t packet_count = 1 + total_len / MAX_PACKET_LENGTH;
reset_packet_write_state(net);
struct io_vec *vec;
uchar *headers;
uchar **compressed_buffers = nullptr;
if (total_len < MAX_PACKET_LENGTH) {
/*
Most writes hit this case, ie, less than MAX_PACKET_LENGTH of
query text.
*/
vec = net_async->inline_async_write_vector;
headers = net_async->inline_async_write_header;
} else {
/* Large query, create the vector and header buffer dynamically. */
vec = (struct io_vec *)my_malloc(
PSI_NOT_INSTRUMENTED, sizeof(struct io_vec) * (packet_count * 2 + 1),
MYF(MY_ZEROFILL));
if (!vec) {
return 0;
}
headers =
(uchar *)my_malloc(PSI_NOT_INSTRUMENTED,
packet_count * (header_len + 1), MYF(MY_ZEROFILL));
if (!headers) {
my_free(vec);
return 0;
}
}
/*
Regardless of where vec and headers come from, these are what we
feed to writev and populate below.
*/
net_async->async_write_vector = vec;
net_async->async_write_headers = headers;
if (net->compress) {
// Will need to hand compress and manage at most 1 buffer per packet
compressed_buffers =
(uchar **)my_malloc(key_memory_NET_compress_packet,
sizeof(uchar *) * packet_count, MYF(MY_ZEROFILL));
if (!compressed_buffers) {
reset_packet_write_state(net);
return 0;
}
}
net_async->compressed_write_buffers = compressed_buffers;
/*
We sneak the command into the first header, so the special casing
below about packet_num == 0 relates to that. This lets us avoid
an extra allocation and copying the input buffers again.
Every chunk of MAX_PACKET_LENGTH results in a header and a
payload, so we have twice as many entries in the IO
vector as we have packet_count. The first packet may be prefixed with a
small amount of data, so that one actually might
consume *three* iovec entries.
*/
for (size_t packet_num = 0; packet_num < packet_count; ++packet_num) {
/*
The first iovec contains the headers only and command if it is provided
*/
uchar *buf = headers + packet_num * (header_len + 1);
size_t bytes_queued = 0;
(*vec).iov_base = buf;
(*vec).iov_len = header_len;
/*
if using compression, add the compression header. Usually, we would rely on
compress_packet to add compression headers, but here we assume
that headers do not compress well due to their short length and send them
as is by constructing our own packat and incrementing compress_pkt_nr
manually.
We don't compress the headers together with the payload because that
would mean extra memcpy's to concatenate the buffers to pass into
compress_packet.
*/
if (net->compress) {
size_t comp_packet_len = NET_HEADER_SIZE;
if (packet_num == 0) {
comp_packet_len += prefix_len + (include_command ? 1 : 0);
}
int3store(buf, comp_packet_len);
buf[3] = (uchar)net->compress_pkt_nr++;
/*
The bytes in COMP_HEADER_SIZE are implicitly zero because they were
zero filled. A zero length means that the contents are uncompressed.
*/
buf += NET_HEADER_SIZE + COMP_HEADER_SIZE;
}
size_t packet_size = min<size_t>(MAX_PACKET_LENGTH, total_len);
int3store(buf, packet_size);
buf[3] = (uchar)net->pkt_nr++;
/*
We sneak the command byte into the header, even though
technically it is payload. This lets us avoid an allocation
or separate one-byte entry in our iovec.
*/
if (packet_num == 0 && include_command) {
buf[4] = command;
(*vec).iov_len++;
/* Our command byte counts against the packet size. */
++bytes_queued;
}
++vec;
/* Second iovec (if any), our optional prefix. */
if (packet_num == 0 && optional_prefix != nullptr) {
(*vec).iov_base = const_cast<uchar *>(optional_prefix);
(*vec).iov_len = prefix_len;
bytes_queued += prefix_len;
++vec;
}
/*
Final iovec, the payload itself. Send however many bytes from
packet we have left, and advance our packet pointer.
*/
const size_t remaining_bytes = packet_size - bytes_queued;
(*vec).iov_base = const_cast<uchar *>(packet);
(*vec).iov_len = remaining_bytes;
bytes_queued += remaining_bytes;
packet += remaining_bytes;
total_len -= bytes_queued;
/* clang-format off */
/*
If we have a payload to compress, then compress_packet will add
compression headers for us. This is what we have at this point where
each line is an iovec.
| len |cpn|uncompress len| len | pn | command |
| prefix + command | 0 |0 | total_len = command + prefix + payload | 0 |COM_* |
| prefix |
|... |
|payload |
|... |
We want to transform into this:
| len |cpn|uncompress len| len | pn | command |
| prefix +command | 0 |0 | total_len = command + prefix + payload | 0 |COM_* |
| prefix |
|... |
| len |cpn|uncompress len| compressed payload |
| len(compressed payload) | 1| len(payload)| compress(payload) |
*/
/* clang-format on */
if (net->compress && remaining_bytes) {
(*vec).iov_base =
compress_packet(net, (uchar *)(*vec).iov_base, &(*vec).iov_len);
if (!(*vec).iov_base) {
reset_packet_write_state(net);
return 0;
}
compressed_buffers[net_async->compressed_buffers_size++] =
(uchar *)(*vec).iov_base;
}
++vec;
/* Make sure we sent entire packets. */
if (total_len > 0) {
assert(packet_size == MAX_PACKET_LENGTH);
}
}
/* Make sure we don't have anything left to send. */
assert(total_len == 0);
net_async->async_write_vector_size = (vec - net_async->async_write_vector);
net_async->async_write_vector_current = 0;
/*
This is needed because the packet reading code in the net_read_packet_header
uses pkt_nr for verification.
*/
if (net->compress) net->pkt_nr = net->compress_pkt_nr;
return 1;
}
static net_async_status net_write_vector_nonblocking(NET *net, ssize_t *res) {
NET_ASYNC *net_async = NET_ASYNC_DATA(net);
struct io_vec *vec =
net_async->async_write_vector + net_async->async_write_vector_current;
DBUG_TRACE;
while (net_async->async_write_vector_current !=
net_async->async_write_vector_size) {
if (vio_is_blocking(net->vio)) {
vio_set_blocking_flag(net->vio, false);
}
*res = vio_write(net->vio, (uchar *)vec->iov_base, vec->iov_len);
if (*res < 0) {
if (socket_errno == SOCKET_EAGAIN ||
(SOCKET_EAGAIN != SOCKET_EWOULDBLOCK &&
socket_errno == SOCKET_EWOULDBLOCK)) {
/*
In the unlikely event that there is a renegotiation and
SSL_ERROR_WANT_READ is returned, set blocking state to read.
*/
if (static_cast<size_t>(*res) == VIO_SOCKET_WANT_READ) {
net_async->async_blocking_state = NET_NONBLOCKING_READ;
} else {
net_async->async_blocking_state = NET_NONBLOCKING_WRITE;
}
return NET_ASYNC_NOT_READY;
}
return NET_ASYNC_COMPLETE;
}
const size_t bytes_written = static_cast<size_t>(*res);
vec->iov_len -= bytes_written;
vec->iov_base = (char *)vec->iov_base + bytes_written;
if (vec->iov_len != 0) break;
++net_async->async_write_vector_current;
vec++;
}
if (net_async->async_write_vector_current ==
net_async->async_write_vector_size) {
return NET_ASYNC_COMPLETE;
}
net_async->async_blocking_state = NET_NONBLOCKING_WRITE;
return NET_ASYNC_NOT_READY;
}
/**
Send a command to the server in asynchronous way. This function will first
populate all headers in NET::async_write_headers, followed by payload in
NET::async_write_vector. Once header and payload is populated in NET, were
call net_write_vector_nonblocking to send the packets to server in an
asynchronous way.
*/
net_async_status net_write_command_nonblocking(NET *net, uchar command,
const uchar *prefix,
size_t prefix_len,
const uchar *packet,
size_t packet_len, bool *res) {
net_async_status status;
NET_ASYNC *net_async = NET_ASYNC_DATA(net);
ssize_t rc;
DBUG_TRACE;
DBUG_DUMP("net write prefix", prefix, prefix_len);
DBUG_DUMP("net write pkt", packet, packet_len);
if (unlikely(!net->vio)) {
/* nowhere to write */
*res = false;
goto done;
}
switch (net_async->async_operation) {
case NET_ASYNC_OP_IDLE:
if (!begin_packet_write_state(net, command, packet, packet_len, prefix,
prefix_len)) {
*res = false;
goto done;
}
net_async->async_operation = NET_ASYNC_OP_WRITING;
[[fallthrough]];
case NET_ASYNC_OP_WRITING:
status = net_write_vector_nonblocking(net, &rc);
if (status == NET_ASYNC_COMPLETE) {
if (rc < 0) {
*res = true;
} else {
*res = false;
}
goto done;
}
return NET_ASYNC_NOT_READY;
default:
assert(false);
*res = true;
return NET_ASYNC_COMPLETE;
}
done:
reset_packet_write_state(net);
net_async->async_operation = NET_ASYNC_OP_IDLE;
return NET_ASYNC_COMPLETE;
}
/*
Non blocking version of my_net_write().
*/
net_async_status my_net_write_nonblocking(NET *net, const uchar *packet,
size_t len, bool *res) {
return net_write_command_nonblocking(net, COM_END, packet, len, nullptr, 0,
res);
}
/**
Send a command to the server.
The reason for having both header and packet is so that libmysql
can easy add a header to a special command (like prepared statements)
without having to re-alloc the string.
As the command is part of the first data packet, we have to do some data
juggling to put the command in there, without having to create a new
packet.
This function will split big packets into sub-packets if needed.
(Each sub packet can only be 2^24 bytes)
@param net NET handler
@param command Command in MySQL server (enum enum_server_command)
@param header Header to write after command
@param head_len Length of header
@param packet Query or parameter to query
@param len Length of packet
@retval
0 ok
@retval
1 error
*/
bool net_write_command(NET *net, uchar command, const uchar *header,
size_t head_len, const uchar *packet, size_t len) {
/* turn off non blocking operations */
if (!vio_is_blocking(net->vio)) vio_set_blocking_flag(net->vio, true);
size_t length = len + 1 + head_len; /* 1 extra byte for command */
uchar buff[NET_HEADER_SIZE + 1];
uint header_size = NET_HEADER_SIZE + 1;
DBUG_TRACE;
DBUG_PRINT("enter", ("length: %lu", (ulong)len));
buff[4] = command; /* For first packet */
if (length >= MAX_PACKET_LENGTH) {
/* Take into account that we have the command in the first header */
len = MAX_PACKET_LENGTH - 1 - head_len;
do {
int3store(buff, MAX_PACKET_LENGTH);
buff[3] = (uchar)net->pkt_nr++;
if (net_write_buff(net, buff, header_size) ||
net_write_buff(net, header, head_len) ||
net_write_buff(net, packet, len)) {
return true;
}
packet += len;
length -= MAX_PACKET_LENGTH;
len = MAX_PACKET_LENGTH;
head_len = 0;
header_size = NET_HEADER_SIZE;
} while (length >= MAX_PACKET_LENGTH);
len = length; /* Data left to be written */
}
int3store(buff, static_cast<uint>(length));
buff[3] = (uchar)net->pkt_nr++;
const bool rc = net_write_buff(net, buff, header_size) ||
(head_len && net_write_buff(net, header, head_len)) ||
net_write_buff(net, packet, len) || net_flush(net);
return rc;
}
/**
Caching the data in a local buffer before sending it.
Fill up net->buffer and send it to the client when full.
If the rest of the to-be-sent-packet is bigger than buffer,
send it in one big block (to avoid copying to internal buffer).
If not, copy the rest of the data to the buffer and return without
sending data.
@param net Network handler
@param packet Packet to send
@param len Length of packet
@note
The cached buffer can be sent as it is with 'net_flush()'.
In this code we have to be careful to not send a packet longer than
MAX_PACKET_LENGTH to net_write_packet() if we are using the compressed
protocol as we store the length of the compressed packet in 3 bytes.
@retval
0 ok
@retval
1 error
*/
static bool net_write_buff(NET *net, const uchar *packet, size_t len) {
DBUG_TRACE;
ulong left_length;
if (net->compress && net->max_packet > MAX_PACKET_LENGTH)
left_length = (ulong)(MAX_PACKET_LENGTH - (net->write_pos - net->buff));
else
left_length = (ulong)(net->buff_end - net->write_pos);
#ifdef DEBUG_DATA_PACKETS
DBUG_DUMP("data", packet, len);
#endif
if (len > left_length) {
if (net->write_pos != net->buff) {
/* Fill up already used packet and write it */
memcpy(net->write_pos, packet, left_length);
if (net_write_packet(net, net->buff,
(size_t)(net->write_pos - net->buff) + left_length))
return true;
net->write_pos = net->buff;
packet += left_length;
len -= left_length;
}
if (net->compress) {
/*
We can't have bigger packets than 16M with compression
Because the uncompressed length is stored in 3 bytes
*/
left_length = MAX_PACKET_LENGTH;
while (len > left_length) {
if (net_write_packet(net, packet, left_length)) return true;
packet += left_length;
len -= left_length;
}
}
if (len > net->max_packet) return net_write_packet(net, packet, len);
/* Send out rest of the blocks as full sized blocks */
}
if (len > 0) memcpy(net->write_pos, packet, len);
net->write_pos += len;
return false;
}
/**
Write a determined number of bytes to a network handler.
@param net NET handler.
@param buf Buffer containing the data to be written.
@param count The length, in bytes, of the buffer.
@return true on error, false on success.
*/
static bool net_write_raw_loop(NET *net, const uchar *buf, size_t count) {
unsigned int retry_count = 0;
while (count) {
const size_t sentcnt = vio_write(net->vio, buf, count);
/* VIO_SOCKET_ERROR (-1) indicates an error. */
if (sentcnt == VIO_SOCKET_ERROR) {
/* A recoverable I/O error occurred? */
if (net_should_retry(net, &retry_count))
continue;