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easy: allow connect-only handle reuse with easy_perform

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- Detach and disconnect an attached connection before performing.

Prior to this change it was not possible to safely reuse an easy handle
with an attached connection in a second call to curl_easy_perform. The
only known case of this is a connect-only type handle where the
connection was detached when curl_easy_perform returned, only to be
reattached by either curl_easy_send/recv.

This commit effectively reverts 2f8ecd5d and be82a360, the latter of
which treated the reuse as an error. Prior to that change undefined
behavior may occur in such a case.

Bug: https://curl.se/mail/lib-2025-01/0044.html
Reported-by: Aleksander Mazur

Closes https://github.com/curl/curl/pull/16008
This commit is contained in:
Jay Satiro 2025-01-15 03:56:11 -05:00
parent f25a807a7d
commit 4f99efb192
4 changed files with 55 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
docs/libcurl/opts/CURLOPT_CONNECT_ONLY.md
View File

@ -34,8 +34,8 @@ and then return.
The option can be used to simply test a connection to a server, but is more
useful when used with the CURLINFO_ACTIVESOCKET(3) option to
curl_easy_getinfo(3) as the library can set up the connection and then the
application can obtain the most recently used socket for special data
curl_easy_getinfo(3) as the library can set up the connection and then
the application can obtain the most recently used socket for special data
transfers.
Since 7.86.0, this option can be set to '2' and if HTTP or WebSocket are used,
@ -43,16 +43,13 @@ libcurl performs the request and reads all response headers before handing
over control to the application.
Transfers marked connect only do not reuse any existing connections and
connections marked connect only are not allowed to get reused. For this
reason, an easy handle cannot be reused for a second transfer when
CURLOPT_CONNECT_ONLY(3) is set, it must be closed with curl_easy_cleanup(3)
once the application is done with it.
connections marked connect only are not allowed to get reused.
If the connect only transfer is done using the multi interface, the particular
easy handle must remain added to the multi handle for as long as the
application wants to use it. Once it has been removed with
curl_multi_remove_handle(3), curl_easy_send(3) and curl_easy_recv(3) do not
function.
curl_multi_remove_handle(3), curl_easy_send(3) and
curl_easy_recv(3) do not function.
# DEFAULT

18
lib/easy.c
View File

@ -751,11 +751,6 @@ static CURLcode easy_perform(struct Curl_easy *data, bool events)
if(!data)
return CURLE_BAD_FUNCTION_ARGUMENT;
if(data->conn) {
failf(data, "cannot use again while associated with a connection");
return CURLE_BAD_FUNCTION_ARGUMENT;
}
if(data->set.errorbuffer)
/* clear this as early as possible */
data->set.errorbuffer[0] = 0;
@ -767,6 +762,19 @@ static CURLcode easy_perform(struct Curl_easy *data, bool events)
return CURLE_FAILED_INIT;
}
/* if the handle has a connection still attached (it is/was a connect-only
handle) then disconnect before performing */
if(data->conn) {
struct connectdata *c;
curl_socket_t s;
Curl_detach_connection(data);
s = Curl_getconnectinfo(data, &c);
if((s != CURL_SOCKET_BAD) && c) {
Curl_cpool_disconnect(data, c, TRUE);
}
DEBUGASSERT(!data->conn);
}
if(data->multi_easy)
multi = data->multi_easy;
else {

24
tests/data/test696
View File

@ -7,7 +7,7 @@ HTTP GET
</info>
<reply>
<data>
<data nocheck="yes">
HTTP/1.1 200 OK swsclose
Server: test-server/fake
Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
@ -38,15 +38,33 @@ http://%HOSTIP:%HTTPPORT
#
# Verify data after the test has been "shot"
<verify>
<stdout>
HTTP/1.1 200 OK swsclose
Server: test-server/fake
Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
Content-Length: 6
Connection: close
-foo-
HTTP/1.1 200 OK swsclose
Server: test-server/fake
Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
Content-Length: 6
Connection: close
-foo-
</stdout>
<protocol>
GET /556 HTTP/1.1
Host: ninja
GET /556 HTTP/1.1
Host: ninja
</protocol>
# 43 == CURLE_BAD_FUNCTION_ARGUMENT
<errorcode>
43
0
</errorcode>
</verify>
</testcase>

23
tests/libtest/lib556.c
View File

@ -41,6 +41,9 @@ CURLcode test(char *URL)
{
CURLcode res;
CURL *curl;
#ifdef LIB696
int transfers = 0;
#endif
if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
fprintf(stderr, "curl_global_init() failed\n");
@ -58,6 +61,10 @@ CURLcode test(char *URL)
test_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
test_setopt(curl, CURLOPT_VERBOSE, 1L);
#ifdef LIB696
again:
#endif
res = curl_easy_perform(curl);
if(!res) {
@ -87,8 +94,12 @@ CURLcode test(char *URL)
if(nread) {
/* send received stuff to stdout */
if(!write(STDOUT_FILENO, buf, nread))
if((size_t)write(STDOUT_FILENO, buf, nread) != nread) {
fprintf(stderr, "write() failed: errno %d (%s)\n",
errno, strerror(errno));
res = TEST_ERR_FAILURE;
break;
}
}
} while((res == CURLE_OK && nread) || (res == CURLE_AGAIN));
@ -98,12 +109,10 @@ CURLcode test(char *URL)
}
#ifdef LIB696
/* attempt to use the handle again */
test_setopt(curl, CURLOPT_URL, URL);
test_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
test_setopt(curl, CURLOPT_VERBOSE, 1L);
res = curl_easy_perform(curl);
++transfers;
/* perform the transfer a second time */
if(!res && transfers == 1)
goto again;
#endif
test_cleanup: