1CURLOPT_ALTSVC_CTRL(3) curl_easy_setopt options CURLOPT_ALTSVC_CTRL(3)
2
3
4
6 CURLOPT_ALTSVC_CTRL - control alt-svc behavior
7
9 #include <curl/curl.h>
10
11 #define CURLALTSVC_IMMEDIATELY (1<<0)
12 #define CURLALTSVC_READONLYFILE (1<<2)
13 #define CURLALTSVC_H1 (1<<3)
14 #define CURLALTSVC_H2 (1<<4)
15 #define CURLALTSVC_H3 (1<<5)
16
17 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC_CTRL, long bitmask);
18
20 Warning: this feature is early code and is marked as experimental. It
21 can only be enabled by explicitly telling configure with --enable-alt-
22 svc. You are advised to not ship this in production before the experi‐
23 mental label is removed.
24
26 Populate the long bitmask with the correct set of features to instruct
27 libcurl how to handle Alt-Svc for the transfers using this handle.
28
29 libcurl will only accept Alt-Svc headers over a secure transport, mean‐
30 ing HTTPS. It will also only complete a request to an alternative ori‐
31 gin if that origin is properly hosted over HTTPS. These requirements
32 are there to make sure both the source and the destination are legiti‐
33 mate.
34
35 Setting any bit will enable the alt-svc engine.
36
37 CURLALTSVC_IMMEDIATELY
38 If an Alt-Svc: header is received, this instructs libcurl to
39 switch to one of those alternatives asap rather than to save it
40 and use for the next request. (Not currently supported).
41
42 CURLALTSVC_READONLYFILE
43 Do not write the alt-svc cache back to the file specified with
44 CURLOPT_ALTSVC(3) even if it gets updated. By default a file
45 specified with that option will be read and written to as deemed
46 necessary.
47
48 CURLALTSVC_H1
49 Accept alternative services offered over HTTP/1.1.
50
51 CURLALTSVC_H2
52 Accept alternative services offered over HTTP/2. This will only
53 be used if libcurl was also built to actually support HTTP/2,
54 otherwise this bit will be ignored.
55
56 CURLALTSVC_H3
57 Accept alternative services offered over HTTP/3. This will only
58 be used if libcurl was also built to actually support HTTP/3,
59 otherwise this bit will be ignored.
60
62 Alt-Svc handling is disabled by default. If CURLOPT_ALTSVC(3) is set,
63 CURLOPT_ALTSVC_CTRL(3) has a default value corresponding to
64 CURLALTSVC_H1 | CURLALTSVC_H2 | CURLALTSVC_H3 - the HTTP/2 and HTTP/3
65 bits are only set if libcurl was built with support for those versions.
66
68 HTTPS
69
71 CURL *curl = curl_easy_init();
72 if(curl) {
73 curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1);
74 curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt");
75 curl_easy_perform(curl);
76 }
77
79 Added in 7.64.1
80
82 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
83 if not.
84
86 CURLOPT_ALTSVC(3), CURLOPT_CONNECT_TO(3), CURLOPT_RESOLVE(3),
87
88
89
90libcurl 7.71.1 February 11, 2020 CURLOPT_ALTSVC_CTRL(3)