CURLOPT_HEADEROPT(3) Library Functions Manual CURLOPT_HEADEROPT(3)

CURLOPT_HEADEROPT - send HTTP headers to both proxy and host or separately

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADEROPT, long bitmask);

Pass a long that is a bitmask of options of how to deal with headers. The two mutually exclusive options are:

CURLHEADER_UNIFIED - the headers specified in CURLOPT_HTTPHEADER(3) are used in requests both to servers and proxies. With this option enabled, CURLOPT_PROXYHEADER(3) does not have any effect.

CURLHEADER_SEPARATE - makes CURLOPT_HTTPHEADER(3) headers only get sent to a server and not to a proxy. Proxy headers must be set with CURLOPT_PROXYHEADER(3) to get used. Note that if a non-CONNECT request is sent to a proxy, libcurl sends both server headers and proxy headers. When doing CONNECT, libcurl sends CURLOPT_PROXYHEADER(3) headers only to the proxy and then CURLOPT_HTTPHEADER(3) headers only to the server.

CURLHEADER_SEPARATE (changed in 7.42.1, used CURLHEADER_UNIFIED before then)

HTTP

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode ret;
    struct curl_slist *list;
    list = curl_slist_append(NULL, "Shoesize: 10");
    list = curl_slist_append(list, "Accept:");
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_PROXY, "http://localhost:8080");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
    /* HTTPS over a proxy makes a separate CONNECT to the proxy, so tell
       libcurl to not send the custom headers to the proxy. Keep them
       separate! */
    curl_easy_setopt(curl, CURLOPT_HEADEROPT, CURLHEADER_SEPARATE);
    ret = curl_easy_perform(curl);
    curl_slist_free_all(list);
    curl_easy_cleanup(curl);
  }
}

Added in 7.37.0

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

CURLOPT_HTTPHEADER(3), CURLOPT_PROXYHEADER(3)

2024-05-22 libcurl