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sendf.c: added ability to call recv() before send() as workaround

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WinSock destroys recv() buffer if send() is failed. As result - server
response may be lost if server sent it while curl is still sending
request. This behavior noticeable on HTTP server short replies if
libcurl use several send() for request (usually for POST request).
To workaround this problem, libcurl use recv() before every send() and
keeps received data in intermediate buffer for further processing.

Fixes: #657
Closes: #668
This commit is contained in:
Karlson2k 2016-02-19 22:38:20 +03:00 • committed by Daniel Stenberg
parent ad3d40d407
commit 72d5e144fb
4 changed files with 179 additions and 1 deletions
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102
lib/sendf.c
View file

@ -33,6 +33,7 @@
#include "non-ascii.h"
#include "curl_printf.h"
#include "strerror.h"
#include "select.h"
/* The last #include files should be: */
#include "curl_memory.h"
@ -120,6 +121,90 @@ static size_t convert_lineends(struct SessionHandle *data,
}
#endif /* CURL_DO_LINEEND_CONV */
#ifdef USE_RECV_BEFORE_SEND_WORKAROUND
static void pre_receive_plain(struct connectdata *conn, int num)
{
const curl_socket_t sockfd = conn->sock[num];
struct postponed_data * const psnd = &(conn->postponed[num]);
size_t bytestorecv = psnd->allocated_size - psnd->recv_size;
/* WinSock will destroy unread received data if send() is
failed.
To avoid lossage of received data, recv() must be
performed before every send() if any incoming data is
available. However, skip this, if buffer is already full. */
if((conn->handler->protocol&PROTO_FAMILY_HTTP) != 0 &&
conn->recv[num] == Curl_recv_plain &&
(!psnd->buffer || bytestorecv)) {
const int readymask = Curl_socket_check(sockfd, CURL_SOCKET_BAD,
CURL_SOCKET_BAD, 0);
if(readymask != -1 && (readymask & CURL_CSELECT_IN) != 0) {
/* Have some incoming data */
if(!psnd->buffer) {
/* Use buffer double default size for intermediate buffer */
psnd->allocated_size = 2 * BUFSIZE;
psnd->buffer = malloc(psnd->allocated_size);
psnd->recv_size = 0;
psnd->recv_processed = 0;
#ifdef DEBUGBUILD
psnd->bindsock = sockfd; /* Used only for DEBUGASSERT */
#endif /* DEBUGBUILD */
bytestorecv = psnd->allocated_size;
}
if(psnd->buffer) {
ssize_t recvedbytes;
DEBUGASSERT(psnd->bindsock == sockfd);
recvedbytes = sread(sockfd, psnd->buffer + psnd->recv_size,
bytestorecv);
if(recvedbytes > 0)
psnd->recv_size += recvedbytes;
}
else
psnd->allocated_size = 0;
}
}
}
static ssize_t get_pre_recved(struct connectdata *conn, int num, char *buf,
size_t len)
{
struct postponed_data * const psnd = &(conn->postponed[num]);
size_t copysize;
if(!psnd->buffer)
return 0;
DEBUGASSERT(psnd->allocated_size > 0);
DEBUGASSERT(psnd->recv_size <= psnd->allocated_size);
DEBUGASSERT(psnd->recv_processed <= psnd->recv_size);
/* Check and process data that already received and storied in internal
intermediate buffer */
if(psnd->recv_size > psnd->recv_processed) {
DEBUGASSERT(psnd->bindsock == conn->sock[num]);
copysize = CURLMIN(len, psnd->recv_size - psnd->recv_processed);
memcpy(buf, psnd->buffer + psnd->recv_processed, copysize);
psnd->recv_processed += copysize;
}
else
copysize = 0; /* buffer was allocated, but nothing was received */
/* Free intermediate buffer if it has no unprocessed data */
if(psnd->recv_processed == psnd->recv_size) {
free(psnd->buffer);
psnd->buffer = NULL;
psnd->allocated_size = 0;
psnd->recv_size = 0;
psnd->recv_processed = 0;
#ifdef DEBUGBUILD
psnd->bindsock = CURL_SOCKET_BAD;
#endif /* DEBUGBUILD */
}
return (ssize_t)copysize;
}
#else /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
/* Use "do-nothing" macros instead of functions when workaround not used */
#define pre_receive_plain(c,n) do {} WHILE_FALSE
#define get_pre_recved(c,n,b,l) 0
#endif /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
/* Curl_infof() is for info message along the way */
void Curl_infof(struct SessionHandle *data, const char *fmt, ...)
@ -255,6 +340,12 @@ ssize_t Curl_send_plain(struct connectdata *conn, int num,
{
curl_socket_t sockfd = conn->sock[num];
ssize_t bytes_written;
/* WinSock will destroy unread received data if send() is
failed.
To avoid lossage of received data, recv() must be
performed before every send() if any incoming data is
available. */
pre_receive_plain(conn, num);
#ifdef MSG_FASTOPEN /* Linux */
if(conn->bits.tcp_fastopen) {
@ -322,7 +413,16 @@ ssize_t Curl_recv_plain(struct connectdata *conn, int num, char *buf,
size_t len, CURLcode *code)
{
curl_socket_t sockfd = conn->sock[num];
ssize_t nread = sread(sockfd, buf, len);
ssize_t nread;
/* Check and return data that already received and storied in internal
intermediate buffer */
nread = get_pre_recved(conn, num, buf, len);
if(nread > 0) {
*code = CURLE_OK;
return nread;
}
nread = sread(sockfd, buf, len);
*code = CURLE_OK;
if(-1 == nread) {