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nuttx/net/tcp/tcp_recvfrom.c
YAMAMOTO Takashi 4878b7729c tcp: simplify readahead 
Do not bother to preserve segment boundaries in the tcp
readahead queues.

* Avoid wasting the tail IOB space for each segments.
  Instead, pack the newly received data into the tail space
  of the last IOB. Also, advertise the tail space as
  a part of the window.

* Use IOB chain directly. Eliminate IOB queue overhead.

* Allow to accept only a part of a segment.

* This change improves the memory efficiency.
  And probably more importantly, allows less-confusing
  recv window advertisement behavior.
  Previously, even when we advertise N bytes window,
  we often couldn't actually accept N bytes. Depending on
  the segment sizes and IOB configurations, it was causing
  segment drops.
  Also, the previous code was moving the right edge of the
  window back and forth too often, even when nothing in
  the system was competing on the IOBs. Shrinking the
  window that way is a kinda well known recipe to confuse
  the peer stack.
2021-06-30 06:22:14 +09:00

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/****************************************************************************
* net/tcp/tcp_recvfrom.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#ifdef CONFIG_NET_TCP
#include <string.h>
#include <errno.h>
#include <debug.h>
#include <assert.h>
#include <nuttx/semaphore.h>
#include <nuttx/net/net.h>
#include <nuttx/mm/iob.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/ip.h>
#include <nuttx/net/tcp.h>
#include "netdev/netdev.h"
#include "devif/devif.h"
#include "tcp/tcp.h"
#include "socket/socket.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define IPv4BUF ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
#define IPv6BUF ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
#define TCPIPv4BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
#define TCPIPv6BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
/****************************************************************************
* Private Types
****************************************************************************/
struct tcp_recvfrom_s
{
FAR struct socket *ir_sock; /* The parent socket structure */
FAR struct devif_callback_s *ir_cb; /* Reference to callback instance */
sem_t ir_sem; /* Semaphore signals recv completion */
size_t ir_buflen; /* Length of receive buffer */
uint8_t *ir_buffer; /* Pointer to receive buffer */
FAR struct sockaddr *ir_from; /* Address of sender */
FAR socklen_t *ir_fromlen; /* Number of bytes allocated for address of sender */
ssize_t ir_recvlen; /* The received length */
int ir_result; /* Success:OK, failure:negated errno */
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: tcp_update_recvlen
*
* Description:
* Update information about space available for new data and update size
* of data in buffer.
*
* Input Parameters:
* pstate recvfrom state structure
* recvlen size of new data appended to buffer
*
* Returned Value:
* None
*
****************************************************************************/
static inline void tcp_update_recvlen(FAR struct tcp_recvfrom_s *pstate,
size_t recvlen)
{
if (pstate->ir_recvlen < 0)
{
pstate->ir_recvlen = 0;
}
pstate->ir_recvlen += recvlen;
pstate->ir_buffer += recvlen;
pstate->ir_buflen -= recvlen;
}
/****************************************************************************
* Name: tcp_recvfrom_newdata
*
* Description:
* Copy the read data from the packet
*
* Input Parameters:
* dev The structure of the network driver that generated the event.
* pstate recvfrom state structure
*
* Returned Value:
* The number of bytes taken from the packet.
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static size_t tcp_recvfrom_newdata(FAR struct net_driver_s *dev,
FAR struct tcp_recvfrom_s *pstate)
{
size_t recvlen;
/* Get the length of the data to return */
if (dev->d_len > pstate->ir_buflen)
{
recvlen = pstate->ir_buflen;
}
else
{
recvlen = dev->d_len;
}
/* Copy the new appdata into the user buffer */
memcpy(pstate->ir_buffer, dev->d_appdata, recvlen);
ninfo("Received %d bytes (of %d)\n", (int)recvlen, (int)dev->d_len);
/* Update the accumulated size of the data read */
tcp_update_recvlen(pstate, recvlen);
return recvlen;
}
/****************************************************************************
* Name: tcp_newdata
*
* Description:
* Copy the read data from the packet
*
* Input Parameters:
* dev The structure of the network driver that generated the event
* pstate recvfrom state structure
*
* Returned Value:
* None.
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static inline uint16_t tcp_newdata(FAR struct net_driver_s *dev,
FAR struct tcp_recvfrom_s *pstate,
uint16_t flags)
{
FAR struct tcp_conn_s *conn = (FAR struct tcp_conn_s *)
pstate->ir_sock->s_conn;
/* Take as much data from the packet as we can */
size_t recvlen = tcp_recvfrom_newdata(dev, pstate);
/* If there is more data left in the packet that we could not buffer, then
* add it to the read-ahead buffers.
*/
if (recvlen < dev->d_len)
{
FAR uint8_t *buffer = (FAR uint8_t *)dev->d_appdata + recvlen;
uint16_t buflen = dev->d_len - recvlen;
uint16_t nsaved;
nsaved = tcp_datahandler(conn, buffer, buflen);
if (nsaved < buflen)
{
nwarn("WARNING: packet data not fully saved "
"(%d/%u/%zu/%u bytes)\n",
buflen - nsaved,
(unsigned int)nsaved,
recvlen,
(unsigned int)dev->d_len);
}
recvlen += nsaved;
}
if (recvlen < dev->d_len)
{
/* Clear the TCP_CLOSE because we effectively dropped the FIN as well.
*/
flags &= ~TCP_CLOSE;
}
net_incr32(conn->rcvseq, recvlen);
/* Indicate no data in the buffer */
dev->d_len = 0;
return flags;
}
/****************************************************************************
* Name: tcp_readahead
*
* Description:
* Copy the read-ahead data from the packet
*
* Input Parameters:
* pstate recvfrom state structure
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static inline void tcp_readahead(struct tcp_recvfrom_s *pstate)
{
FAR struct tcp_conn_s *conn =
(FAR struct tcp_conn_s *)pstate->ir_sock->s_conn;
FAR struct iob_s *iob;
int recvlen;
/* Check there is any TCP data already buffered in a read-ahead
* buffer.
*/
while ((iob = conn->readahead) != NULL &&
pstate->ir_buflen > 0)
{
DEBUGASSERT(iob->io_pktlen > 0);
/* Transfer that buffered data from the I/O buffer chain into
* the user buffer.
*/
recvlen = iob_copyout(pstate->ir_buffer, iob, pstate->ir_buflen, 0);
ninfo("Received %d bytes (of %d)\n", recvlen, iob->io_pktlen);
/* Update the accumulated size of the data read */
tcp_update_recvlen(pstate, recvlen);
/* If we took all of the data from the I/O buffer chain is empty, then
* release it. If there is still data available in the I/O buffer
* chain, then just trim the data that we have taken from the
* beginning of the I/O buffer chain.
*/
if (recvlen >= iob->io_pktlen)
{
/* Free free the I/O buffer chain */
iob_free_chain(iob, IOBUSER_NET_TCP_READAHEAD);
conn->readahead = NULL;
}
else
{
/* The bytes that we have received from the head of the I/O
* buffer chain.
*/
conn->readahead = iob_trimhead(iob, recvlen,
IOBUSER_NET_TCP_READAHEAD);
}
}
}
/****************************************************************************
* Name: tcp_sender
*
* Description:
* Getting the sender's address from the UDP packet
*
* Input Parameters:
* dev - The device driver data structure
* pstate - the recvfrom state structure
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked
*
****************************************************************************/
static inline void tcp_sender(FAR struct net_driver_s *dev,
FAR struct tcp_recvfrom_s *pstate)
{
/* Get the family from the packet type, IP address from the IP header, and
* the port number from the TCP header.
*/
#ifdef CONFIG_NET_IPv6
#ifdef CONFIG_NET_IPv4
if (IFF_IS_IPv6(dev->d_flags))
#endif
{
FAR struct sockaddr_in6 *infrom =
(FAR struct sockaddr_in6 *)pstate->ir_from;
if (infrom)
{
FAR struct tcp_hdr_s *tcp = TCPIPv6BUF;
FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
infrom->sin6_family = AF_INET6;
infrom->sin6_port = tcp->srcport;
net_ipv6addr_copy(infrom->sin6_addr.s6_addr, ipv6->srcipaddr);
}
}
#endif /* CONFIG_NET_IPv6 */
#ifdef CONFIG_NET_IPv4
#ifdef CONFIG_NET_IPv6
else
#endif
{
FAR struct sockaddr_in *infrom =
(FAR struct sockaddr_in *)pstate->ir_from;
if (infrom)
{
FAR struct tcp_hdr_s *tcp = TCPIPv4BUF;
FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
infrom->sin_family = AF_INET;
infrom->sin_port = tcp->srcport;
net_ipv4addr_copy(infrom->sin_addr.s_addr,
net_ip4addr_conv32(ipv4->srcipaddr));
memset(infrom->sin_zero, 0, sizeof(infrom->sin_zero));
}
}
#endif /* CONFIG_NET_IPv4 */
}
/****************************************************************************
* Name: tcp_recvhandler
*
* Description:
* This function is called with the network locked to perform the actual
* TCP receive operation via by the lower, device interfacing layer.
*
* Input Parameters:
* dev The structure of the network driver that generated the event.
* pvconn The connection structure associated with the socket
* flags Set of events describing why the callback was invoked
*
* Returned Value:
* None
*
* Assumptions:
* The network is locked.
*
****************************************************************************/
static uint16_t tcp_recvhandler(FAR struct net_driver_s *dev,
FAR void *pvconn, FAR void *pvpriv,
uint16_t flags)
{
FAR struct tcp_recvfrom_s *pstate = (struct tcp_recvfrom_s *)pvpriv;
#if 0 /* REVISIT: The assertion fires. Why? */
FAR struct tcp_conn_s *conn = (FAR struct tcp_conn_s *)pvconn;
/* The TCP socket is connected and, hence, should be bound to a device.
* Make sure that the polling device is the own that we are bound to.
*/
DEBUGASSERT(conn->dev == NULL || conn->dev == dev);
if (conn->dev != NULL && conn->dev != dev)
{
return flags;
}
#endif
ninfo("flags: %04x\n", flags);
/* 'priv' might be null in some race conditions (?) */
if (pstate)
{
/* If new data is available, then complete the read action. */
if ((flags & TCP_NEWDATA) != 0)
{
/* Copy the data from the packet (saving any unused bytes from the
* packet in the read-ahead buffer).
*/
flags = tcp_newdata(dev, pstate, flags);
/* Save the sender's address in the caller's 'from' location */
tcp_sender(dev, pstate);
/* Indicate that the data has been consumed and that an ACK
* should be sent.
*/
flags = (flags & ~TCP_NEWDATA) | TCP_SNDACK;
/* Check for transfer complete. We will consider the
* TCP/IP transfer complete as soon as any data has been received.
* This is safe because if any additional data is received, it
* will be retained in the TCP/IP read-ahead buffer until the
* next receive is performed.
*/
if (pstate->ir_recvlen > 0)
{
ninfo("TCP resume\n");
/* The TCP receive buffer is non-empty. Return now and don't
* allow any further TCP call backs.
*/
pstate->ir_cb->flags = 0;
pstate->ir_cb->priv = NULL;
pstate->ir_cb->event = NULL;
/* Wake up the waiting thread, returning the number of bytes
* actually read.
*/
nxsem_post(&pstate->ir_sem);
}
}
/* Check for a loss of connection.
*
* TCP_DISCONN_EVENTS:
* TCP_CLOSE: The remote host has closed the connection
* TCP_ABORT: The remote host has aborted the connection
* TCP_TIMEDOUT: Connection aborted due to too many retransmissions.
* NETDEV_DOWN: The network device went down
*/
else if ((flags & TCP_DISCONN_EVENTS) != 0)
{
FAR struct socket *psock = pstate->ir_sock;
nwarn("WARNING: Lost connection\n");
/* We could get here recursively through the callback actions of
* tcp_lost_connection(). So don't repeat that action if we have
* already been disconnected.
*/
DEBUGASSERT(psock != NULL);
if (_SS_ISCONNECTED(psock->s_flags))
{
/* Handle loss-of-connection event */
tcp_lost_connection(psock, pstate->ir_cb, flags);
}
/* Check if the peer gracefully closed the connection. */
if ((flags & TCP_CLOSE) != 0)
{
/* This case should always return success (zero)! The value of
* ir_recvlen, if zero, will indicate that the connection was
* gracefully closed.
*/
pstate->ir_result = 0;
}
else
{
pstate->ir_result = -ENOTCONN;
}
/* Wake up the waiting thread */
nxsem_post(&pstate->ir_sem);
}
}
return flags;
}
/****************************************************************************
* Name: tcp_recvfrom_initialize
*
* Description:
* Initialize the state structure
*
* Input Parameters:
* psock Pointer to the socket structure for the socket
* buf Buffer to receive data
* len Length of buffer
* pstate A pointer to the state structure to be initialized
*
* Returned Value:
* None
*
* Assumptions:
*
****************************************************************************/
static void tcp_recvfrom_initialize(FAR struct socket *psock, FAR void *buf,
size_t len, FAR struct sockaddr *infrom,
FAR socklen_t *fromlen,
FAR struct tcp_recvfrom_s *pstate)
{
/* Initialize the state structure. */
memset(pstate, 0, sizeof(struct tcp_recvfrom_s));
/* This semaphore is used for signaling and, hence, should not have
* priority inheritance enabled.
*/
nxsem_init(&pstate->ir_sem, 0, 0); /* Doesn't really fail */
nxsem_set_protocol(&pstate->ir_sem, SEM_PRIO_NONE);
pstate->ir_buflen = len;
pstate->ir_buffer = buf;
pstate->ir_from = infrom;
pstate->ir_fromlen = fromlen;
/* Set up the start time for the timeout */
pstate->ir_sock = psock;
}
/* The only un-initialization that has to be performed is destroying the
* semaphore.
*/
#define tcp_recvfrom_uninitialize(s) nxsem_destroy(&(s)->ir_sem)
/****************************************************************************
* Name: tcp_recvfrom_result
*
* Description:
* Evaluate the result of the recv operations
*
* Input Parameters:
* result The result of the net_timedwait operation (may indicate EINTR)
* pstate A pointer to the state structure to be initialized
*
* Returned Value:
* The result of the recv operation with errno set appropriately
*
* Assumptions:
*
****************************************************************************/
static ssize_t tcp_recvfrom_result(int result, struct tcp_recvfrom_s *pstate)
{
/* Check for a error/timeout detected by the event handler. Errors are
* signaled by negative errno values for the rcv length
*/
if (pstate->ir_result < 0)
{
/* This might return EAGAIN on a timeout or ENOTCONN on loss of
* connection (TCP only)
*/
return pstate->ir_result;
}
/* If net_timedwait failed, then we were probably reawakened by a signal.
* In this case, net_timedwait will have returned negated errno
* appropriately.
*/
if (result < 0)
{
return result;
}
return pstate->ir_recvlen;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: psock_tcp_recvfrom
*
* Description:
* Perform the recvfrom operation for a TCP/IP SOCK_STREAM
*
* Input Parameters:
* psock Pointer to the socket structure for the SOCK_DRAM socket
* buf Buffer to receive data
* len Length of buffer
* flags Receive flags
* from INET address of source (may be NULL)
* fromlen The length of the address structure
*
* Returned Value:
* On success, returns the number of characters received. On error,
* -errno is returned (see recvfrom for list of errnos).
*
* Assumptions:
*
****************************************************************************/
ssize_t psock_tcp_recvfrom(FAR struct socket *psock, FAR void *buf,
size_t len, int flags, FAR struct sockaddr *from,
FAR socklen_t *fromlen)
{
struct tcp_recvfrom_s state;
FAR struct tcp_conn_s *conn;
int ret;
net_lock();
conn = (FAR struct tcp_conn_s *)psock->s_conn;
/* Initialize the state structure. This is done with the network locked
* because we don't want anything to happen until we are ready.
*/
tcp_recvfrom_initialize(psock, buf, len, from, fromlen, &state);
/* Handle any any TCP data already buffered in a read-ahead buffer. NOTE
* that there may be read-ahead data to be retrieved even after the
* socket has been disconnected.
*/
tcp_readahead(&state);
/* The default return value is the number of bytes that we just copied
* into the user buffer. We will return this if the socket has become
* disconnected or if the user request was completely satisfied with
* data from the readahead buffers.
*/
ret = state.ir_recvlen;
/* Verify that the SOCK_STREAM has been and still is connected */
if (!_SS_ISCONNECTED(psock->s_flags))
{
/* Was any data transferred from the readahead buffer after we were
* disconnected? If so, then return the number of bytes received. We
* will wait to return end disconnection indications the next time that
* recvfrom() is called.
*
* If no data was received (i.e., ret == 0 -- it will not be
* negative) and the connection was gracefully closed by the remote
* peer, then return success. If ir_recvlen is zero, the caller of
* recvfrom() will get an end-of-file indication.
*/
if (ret <= 0 && !_SS_ISCLOSED(psock->s_flags))
{
/* Nothing was previously received from the read-ahead buffers.
* The SOCK_STREAM must be (re-)connected in order to receive any
* additional data.
*/
ret = -ENOTCONN;
}
}
/* In general, this implementation will not support non-blocking socket
* operations... except in a few cases: Here for TCP receive with read-
* ahead enabled. If this socket is configured as non-blocking then
* return EAGAIN if no data was obtained from the read-ahead buffers.
*/
else if (_SS_ISNONBLOCK(psock->s_flags) || (flags & MSG_DONTWAIT) != 0)
{
/* Return the number of bytes read from the read-ahead buffer if
* something was received (already in 'ret'); EAGAIN if not.
*/
if (ret <= 0)
{
/* Nothing was received */
ret = -EAGAIN;
}
}
/* It is okay to block if we need to. If there is space to receive
* anything more, then we will wait to receive the data. Otherwise return
* the number of bytes read from the read-ahead buffer (already in 'ret').
*/
else
/* We get here when we we decide that we need to setup the wait for
* incoming TCP/IP data. Just a few more conditions to check:
*
* 1) Make sure thet there is buffer space to receive additional data
* (state.ir_buflen > 0). This could be zero, for example, we filled
* the user buffer with data from the read-ahead buffers. And
* 2) then we not want to wait if we already obtained some data from the
* read-ahead buffer. In that case, return now with what we have (don't
* want for more because there may be no timeout).
*/
if (state.ir_recvlen == 0 && state.ir_buflen > 0)
{
/* Set up the callback in the connection */
state.ir_cb = tcp_callback_alloc(conn);
if (state.ir_cb)
{
state.ir_cb->flags = (TCP_NEWDATA | TCP_DISCONN_EVENTS);
state.ir_cb->priv = (FAR void *)&state;
state.ir_cb->event = tcp_recvhandler;
/* Wait for either the receive to complete or for an error/timeout
* to occur. net_timedwait will also terminate if a signal isi
* received.
*/
ret = net_timedwait(&state.ir_sem, _SO_TIMEOUT(psock->s_rcvtimeo));
if (ret == -ETIMEDOUT)
{
ret = -EAGAIN;
}
/* Make sure that no further events are processed */
tcp_callback_free(conn, state.ir_cb);
ret = tcp_recvfrom_result(ret, &state);
}
else
{
ret = -EBUSY;
}
}
/* Receive additional data from read-ahead buffer, send the ACK timely.
*
* Revisit: Because IOBs are system-wide resources, consuming the read
* ahead buffer would update recv window of all connections in the system,
* not only this particular connection.
*/
if (tcp_should_send_recvwindow(conn))
{
netdev_txnotify_dev(conn->dev);
}
net_unlock();
tcp_recvfrom_uninitialize(&state);
return (ssize_t)ret;
}
#endif /* CONFIG_NET_TCP */
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