CURLOPT_ALTSVC_CTRL(3) curl_easy_setopt options CURLOPT_ALTSVC_CTRL(3)
NAME
CURLOPT_ALTSVC_CTRL - control alt-svc behavior
SYNOPSIS
#include <curl/curl.h>
#define CURLALTSVC_READONLYFILE (1<<2)
#define CURLALTSVC_H1 (1<<3)
#define CURLALTSVC_H2 (1<<4)
#define CURLALTSVC_H3 (1<<5)
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC_CTRL, long bitmask);
DESCRIPTION
Populate the long bitmask with the correct set of features to instruct
libcurl how to handle Alt-Svc for the transfers using this handle.
libcurl only accepts Alt-Svc headers over a secure transport, meaning
HTTPS. It will also only complete a request to an alternative origin if
that origin is properly hosted over HTTPS. These requirements are there
to make sure both the source and the destination are legitimate.
Alternative services are only used when setting up new connections. If
there exists an existing connection to the host in the connection pool,
then that will be preferred.
Setting any bit will enable the alt-svc engine.
CURLALTSVC_READONLYFILE
Do not write the alt-svc cache back to the file specified with
CURLOPT_ALTSVC(3) even if it gets updated. By default a file
specified with that option will be read and written to as deemed
necessary.
CURLALTSVC_H1
Accept alternative services offered over HTTP/1.1.
CURLALTSVC_H2
Accept alternative services offered over HTTP/2. This will only
be used if libcurl was also built to actually support HTTP/2,
otherwise this bit will be ignored.
CURLALTSVC_H3
Accept alternative services offered over HTTP/3. This will only
be used if libcurl was also built to actually support HTTP/3,
otherwise this bit will be ignored.
DEFAULT
Alt-Svc handling is disabled by default. If CURLOPT_ALTSVC(3) is set,
CURLOPT_ALTSVC_CTRL(3) has a default value corresponding to
CURLALTSVC_H1 | CURLALTSVC_H2 | CURLALTSVC_H3 - the HTTP/2 and HTTP/3
bits are only set if libcurl was built with support for those versions.
PROTOCOLS
HTTPS
EXAMPLE
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1);
curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt");
curl_easy_perform(curl);
}
AVAILABILITY
Added in 7.64.1
RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
if not.
SEE ALSO
CURLOPT_ALTSVC(3), CURLOPT_CONNECT_TO(3), CURLOPT_RESOLVE(3),
libcurl 7.81.0 November 04, 2021 CURLOPT_ALTSVC_CTRL(3)
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