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multi: implement wait using winsock events 

This avoids using a pair of TCP ports to provide wakeup functionality
for every multi instance on Windows, where socketpair() is emulated
using a TCP socket on loopback which could in turn lead to socket
resource exhaustion.

Reviewed-by: Gergely Nagy
Reviewed-by: Marc Hörsken

Closes #5397
This commit is contained in:
rcombs 2020-05-13 18:49:57 -05:00 committed by Marc Hoersken
parent 477a4e31d7
commit 8bc25c590e
No known key found for this signature in database
GPG Key ID: 61E03CBED7BC859E
2 changed files with 122 additions and 4 deletions
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122
lib/multi.c
View File

@ -374,6 +374,11 @@ struct Curl_multi *Curl_multi_handle(int hashsize, /* socket hash */
multi->max_concurrent_streams = 100;
multi->ipv6_works = Curl_ipv6works(NULL);
#ifdef USE_WINSOCK
multi->wsa_event = WSACreateEvent();
if(multi->wsa_event == WSA_INVALID_EVENT)
goto error;
#else
#ifdef ENABLE_WAKEUP
if(Curl_socketpair(AF_UNIX, SOCK_STREAM, 0, multi->wakeup_pair) < 0) {
multi->wakeup_pair[0] = CURL_SOCKET_BAD;
@ -386,6 +391,7 @@ struct Curl_multi *Curl_multi_handle(int hashsize, /* socket hash */
multi->wakeup_pair[0] = CURL_SOCKET_BAD;
multi->wakeup_pair[1] = CURL_SOCKET_BAD;
}
#endif
#endif
return multi;
@ -1067,11 +1073,15 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
unsigned int i;
unsigned int nfds = 0;
unsigned int curlfds;
bool ufds_malloc = FALSE;
long timeout_internal;
int retcode = 0;
#ifndef USE_WINSOCK
struct pollfd a_few_on_stack[NUM_POLLS_ON_STACK];
struct pollfd *ufds = &a_few_on_stack[0];
bool ufds_malloc = FALSE;
#else
DEBUGASSERT(multi->wsa_event != WSA_INVALID_EVENT);
#endif
if(!GOOD_MULTI_HANDLE(multi))
return CURLM_BAD_HANDLE;
@ -1117,11 +1127,16 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
nfds += extra_nfds; /* add the externally provided ones */
#ifdef ENABLE_WAKEUP
#ifdef USE_WINSOCK
if(use_wakeup) {
#else
if(use_wakeup && multi->wakeup_pair[0] != CURL_SOCKET_BAD) {
#endif
++nfds;
}
#endif
#ifndef USE_WINSOCK
if(nfds > NUM_POLLS_ON_STACK) {
/* 'nfds' is a 32 bit value and 'struct pollfd' is typically 8 bytes
big, so at 2^29 sockets this value might wrap. When a process gets
@ -1132,7 +1147,9 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
return CURLM_OUT_OF_MEMORY;
ufds_malloc = TRUE;
}
nfds = 0;
#endif
/* only do the second loop if we found descriptors in the first stage run
above */
@ -1145,22 +1162,36 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
for(i = 0; i< MAX_SOCKSPEREASYHANDLE; i++) {
curl_socket_t s = CURL_SOCKET_BAD;
#ifdef USE_WINSOCK
long mask = 0;
#endif
if(bitmap & GETSOCK_READSOCK(i)) {
#ifdef USE_WINSOCK
mask |= FD_READ;
#else
ufds[nfds].fd = sockbunch[i];
ufds[nfds].events = POLLIN;
++nfds;
#endif
s = sockbunch[i];
}
if(bitmap & GETSOCK_WRITESOCK(i)) {
#ifdef USE_WINSOCK
mask |= FD_WRITE;
#else
ufds[nfds].fd = sockbunch[i];
ufds[nfds].events = POLLOUT;
++nfds;
#endif
s = sockbunch[i];
}
if(s == CURL_SOCKET_BAD) {
break;
}
#ifdef USE_WINSOCK
if(WSAEventSelect(s, multi->wsa_event, mask) != 0)
return CURLM_INTERNAL_ERROR;
#endif
}
data = data->next; /* check next handle */
@ -1169,6 +1200,17 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
/* Add external file descriptions from poll-like struct curl_waitfd */
for(i = 0; i < extra_nfds; i++) {
#ifdef USE_WINSOCK
long events = 0;
if(extra_fds[i].events & CURL_WAIT_POLLIN)
events |= FD_READ;
if(extra_fds[i].events & CURL_WAIT_POLLPRI)
events |= FD_OOB;
if(extra_fds[i].events & CURL_WAIT_POLLOUT)
events |= FD_WRITE;
if(WSAEventSelect(extra_fds[i].fd, multi->wsa_event, events) != 0)
return CURLM_INTERNAL_ERROR;
#else
ufds[nfds].fd = extra_fds[i].fd;
ufds[nfds].events = 0;
if(extra_fds[i].events & CURL_WAIT_POLLIN)
@ -1178,28 +1220,61 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
if(extra_fds[i].events & CURL_WAIT_POLLOUT)
ufds[nfds].events |= POLLOUT;
++nfds;
#endif
}
#ifdef ENABLE_WAKEUP
#ifndef USE_WINSOCK
if(use_wakeup && multi->wakeup_pair[0] != CURL_SOCKET_BAD) {
ufds[nfds].fd = multi->wakeup_pair[0];
ufds[nfds].events = POLLIN;
++nfds;
}
#endif
#endif
if(nfds) {
int pollrc;
/* wait... */
#ifdef USE_WINSOCK
DWORD waitrc = WSAWaitForMultipleEvents(1, &multi->wsa_event, FALSE,
timeout_ms, FALSE);
/* WSA_WAIT_EVENT_0 is 0, so waitrc >= WSA_WAIT_EVENT_0 warns */
if(waitrc == WSA_WAIT_EVENT_0)
pollrc = 1;
else
pollrc = -1;
#else
pollrc = Curl_poll(ufds, nfds, timeout_ms);
#endif
if(pollrc > 0) {
#ifdef USE_WINSOCK
retcode = 0;
#else
retcode = pollrc;
#endif
/* copy revents results from the poll to the curl_multi_wait poll
struct, the bit values of the actual underlying poll() implementation
may not be the same as the ones in the public libcurl API! */
for(i = 0; i < extra_nfds; i++) {
unsigned short mask = 0;
#ifdef USE_WINSOCK
WSANETWORKEVENTS events = {0};
if(WSAEnumNetworkEvents(extra_fds[i].fd, multi->wsa_event,
&events) == 0) {
if(events.lNetworkEvents & FD_READ)
mask |= CURL_WAIT_POLLIN;
if(events.lNetworkEvents & FD_WRITE)
mask |= CURL_WAIT_POLLOUT;
if(events.lNetworkEvents & FD_OOB)
mask |= CURL_WAIT_POLLPRI;
if(events.lNetworkEvents != 0)
retcode++;
}
WSAEventSelect(extra_fds[i].fd, multi->wsa_event, 0);
#else
unsigned r = ufds[curlfds + i].revents;
if(r & POLLIN)
@ -1208,10 +1283,39 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
mask |= CURL_WAIT_POLLOUT;
if(r & POLLPRI)
mask |= CURL_WAIT_POLLPRI;
#endif
extra_fds[i].revents = mask;
}
#ifdef USE_WINSOCK
/* Count up all our own sockets that had activity,
and remove them from the event. */
if(curlfds) {
data = multi->easyp;
while(data) {
bitmap = multi_getsock(data, sockbunch);
for(i = 0; i < MAX_SOCKSPEREASYHANDLE; i++) {
if(bitmap & (GETSOCK_READSOCK(i) | GETSOCK_WRITESOCK(i))) {
WSANETWORKEVENTS events = {0};
if(WSAEnumNetworkEvents(sockbunch[i], multi->wsa_event,
&events) == 0) {
if(events.lNetworkEvents != 0)
retcode++;
}
WSAEventSelect(sockbunch[i], multi->wsa_event, 0);
}
else
break;
}
data = data->next;
}
}
WSAResetEvent(multi->wsa_event);
#else
#ifdef ENABLE_WAKEUP
if(use_wakeup && multi->wakeup_pair[0] != CURL_SOCKET_BAD) {
if(ufds[curlfds + extra_nfds].revents & POLLIN) {
@ -1224,10 +1328,8 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
when there is no more data, breaking the loop. */
nread = sread(multi->wakeup_pair[0], buf, sizeof(buf));
if(nread <= 0) {
#ifndef USE_WINSOCK
if(nread < 0 && EINTR == SOCKERRNO)
continue;
#endif
break;
}
}
@ -1235,12 +1337,15 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
retcode--;
}
}
#endif
#endif
}
}
#ifndef USE_WINSOCK
if(ufds_malloc)
free(ufds);
#endif
if(ret)
*ret = retcode;
if(!extrawait || nfds)
@ -1295,6 +1400,10 @@ CURLMcode curl_multi_wakeup(struct Curl_multi *multi)
return CURLM_BAD_HANDLE;
#ifdef ENABLE_WAKEUP
#ifdef USE_WINSOCK
if(WSASetEvent(multi->wsa_event))
return CURLM_OK;
#else
/* the wakeup_pair variable is only written during init and cleanup,
making it safe to access from another thread after the init part
and before cleanup */
@ -1327,6 +1436,7 @@ CURLMcode curl_multi_wakeup(struct Curl_multi *multi)
return CURLM_OK;
}
}
#endif
#endif
return CURLM_WAKEUP_FAILURE;
}
@ -2485,9 +2595,13 @@ CURLMcode curl_multi_cleanup(struct Curl_multi *multi)
Curl_hash_destroy(&multi->hostcache);
Curl_psl_destroy(&multi->psl);
#ifdef USE_WINSOCK
WSACloseEvent(multi->wsa_event);
#else
#ifdef ENABLE_WAKEUP
sclose(multi->wakeup_pair[0]);
sclose(multi->wakeup_pair[1]);
#endif
#endif
free(multi);

4
lib/multihandle.h
View File

@ -138,9 +138,13 @@ struct Curl_multi {
previous callback */
unsigned int max_concurrent_streams;
#ifdef USE_WINSOCK
WSAEVENT wsa_event; /* winsock event used for waits */
#else
#ifdef ENABLE_WAKEUP
curl_socket_t wakeup_pair[2]; /* socketpair() used for wakeup
0 is used for read, 1 is used for write */
#endif
#endif
/* multiplexing wanted */
bool multiplexing;