Changing the hostname in libcurl in C - c

Question

I'm trying to play with libcurl SMTP and everything works fine with this example: http://curl.haxx.se/libcurl/c/smtp-mail.html
#include <stdio.h>
#include <string.h>
#include <curl/curl.h>
/* This is a simple example showing how to send mail using libcurl's SMTP
* capabilities. For an exmaple of using the multi interface please see
* smtp-multi.c.
*
* Note that this example requires libcurl 7.20.0 or above.
*/
#define FROM "<sender#example.org>"
#define TO "<addressee#example.net>"
#define CC "<info#example.org>"
static const char *payload_text[] = {
"Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n",
"To: " TO "\r\n",
"From: " FROM "(Example User)\r\n",
"Cc: " CC "(Another example User)\r\n",
"Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd#rfcpedant.example.org>\r\n",
"Subject: SMTP example message\r\n",
"\r\n", /* empty line to divide headers from body, see RFC5322 */
"The body of the message starts here.\r\n",
"\r\n",
"It could be a lot of lines, could be MIME encoded, whatever.\r\n",
"Check RFC5322.\r\n",
NULL
};
struct upload_status {
int lines_read;
};
static size_t payload_source(void *ptr, size_t size, size_t nmemb, void *userp)
{
struct upload_status *upload_ctx = (struct upload_status *)userp;
const char *data;
if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
return 0;
}
data = payload_text[upload_ctx->lines_read];
if(data) {
size_t len = strlen(data);
memcpy(ptr, data, len);
upload_ctx->lines_read++;
return len;
}
return 0;
}
int main(void)
{
CURL *curl;
CURLcode res = CURLE_OK;
struct curl_slist *recipients = NULL;
struct upload_status upload_ctx;
upload_ctx.lines_read = 0;
curl = curl_easy_init();
if(curl) {
/* This is the URL for your mailserver */
curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.com");
/* Note that this option isn't strictly required, omitting it will result in
* libcurl sending the MAIL FROM command with empty sender data. All
* autoresponses should have an empty reverse-path, and should be directed
* to the address in the reverse-path which triggered them. Otherwise, they
* could cause an endless loop. See RFC 5321 Section 4.5.5 for more details.
*/
curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM);
/* Add two recipients, in this particular case they correspond to the
* To: and Cc: addressees in the header, but they could be any kind of
* recipient. */
recipients = curl_slist_append(recipients, TO);
recipients = curl_slist_append(recipients, CC);
curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
/* We're using a callback function to specify the payload (the headers and
* body of the message). You could just use the CURLOPT_READDATA option to
* specify a FILE pointer to read from. */
curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
/* Send the message */
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
/* Free the list of recipients */
curl_slist_free_all(recipients);
/* curl won't send the QUIT command until you call cleanup, so you should be
* able to re-use this connection for additional messages (setting
* CURLOPT_MAIL_FROM and CURLOPT_MAIL_RCPT as required, and calling
* curl_easy_perform() again. It may not be a good idea to keep the
* connection open for a very long time though (more than a few minutes may
* result in the server timing out the connection), and you do want to clean
* up in the end.
*/
curl_easy_cleanup(curl);
}
return (int)res;
}
The email which I send looks like this:
Return-Path: ...
Received: from Hostname (ip)
...
Date:...
Subject:...
...
But how could I change my own hostname from libcurl. Is it possible to send it in the header or something like this? Or I only could change it by adding the lines in /etc/hostname file?