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Daniel Stenberg 57a94fec47

The two bitmask constants for *CLEAR_DNS and *CLEAR_CONNS were
duplicates (both set to 1), so they cannot be distinguished and both
actions fire.

This shipped in public releases since 8.16.0 to and include 8.19.0.

This fix adds CURLMNWC_CLEAR_ALL to be the new 1, and it now implies all
bits. The DNS and CONNS defines get two new bits (2, 4).

Follow-up to 55c045c863

Found by Codex Security
Closes #20968

2026-03-22 18:06:32 +01:00

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SPDX-License-Identifier

Title

Section

Source

See-also

Protocol

Added-in

curl

CURLMOPT_NETWORK_CHANGED

libcurl

CURLOPT_FRESH_CONNECT (3)

CURLOPT_FORBID_REUSE (3)

All

8.16.0

NAME

CURLMOPT_NETWORK_CHANGED - signal network changed

SYNOPSIS

#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_NETWORK_CHANGED,
                            long value);

DESCRIPTION

Pass a long with a bitmask to tell libcurl how the multi handle should react. The following values in the mask are defined. All bits not mentioned are reserved for future extensions.

This option can be set at any time and repeatedly. Each call only affects the currently cached connections and DNS information. Any connection created or DNS information added afterwards is cached the usual way again. Phrasing it another way: the option is not persisted but setting it serves as a "trigger" to clear the caches.

The call affects only the connection and DNS cache of the multi handle itself and not the ones owned by SHARE handles.

CURLMNWC_CLEAR_ALL

Clear everything. (Added in 8.20.0)

CURLMNWC_CLEAR_CONNS

No longer reuse any existing connection in the multi handle's connection cache. This closes all connections that are not in use. Ongoing transfers continue on the connections they operate on.

CURLMNWC_CLEAR_DNS

Clear the multi handle's DNS cache. Ongoing transfers keep using their already resolved addresses, but future name resolutions are performed again.

DEFAULT

0, which has no effect.

%PROTOCOLS%

EXAMPLE

int main(void)
{
  CURLM *m = curl_multi_init();
  /* do transfers on the multi handle */
  /* do not reuse existing connections */
  curl_multi_setopt(m, CURLMOPT_NETWORK_CHANGED, CURLMNWC_CLEAR_CONNS);
}

%AVAILABILITY%

RETURN VALUE

curl_multi_setopt(3) returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

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