Fast(est) way to get X-Forwarded-for in header with G-Wan?

Question

Since this non-RFC header field isn't in HTTP_Env nor http_t struct, i wrote this snippet :

  //Get reply buffer
  xbuf_t *reply = get_reply(argv);

  // Init & create json buffer
  xbuf_t json_buf;
  xbuf_init(&json_buf);
  jsn_t *params = jsn_add_node(0, "params");

  [...]

  http_t *http = (http_t*)get_env(argv, HTTP_HEADERS);
  xbuf_t *read_buf  = (xbuf_t*)get_env(argv, READ_XBUF);

  [...]

  // Add remote ip (from X-Forwarded-for or REMOTE_ADDR)
  char *xforward = xbuf_findstr(read_buf, "X-Forwarded-For:");
  if(xforward) {
    jsn_add_string(params, "ip", xforward);
  } else {
    jsn_add_string(params, "ip", get_env(argv, REMOTE_ADDR));
  }

The json part is, of course, part of the application and irrelevant with the question. Do you think it's a right way to do it or is xbuf_findstr() inefficient and there is a faster solution (without using ASM or cryptic code) ?

Thank you :)

EDIT : Wow, i forgot the strok() part to get rid of the first field, i just want the ip adress of course.

EDIT2 : Patched version with strtok

  // Add remote ip (from X-Forwarded-for or REMOTE_ADDR)
  char *xforward = xbuf_findstr(read_buf, "X-Forwarded-For: ");
  if(xforward) {
    gc_init(argv, 1024);
    char *copy = gc_malloc(argv, strlen(xforward)+ 1);
    memcpy(copy, xforward, strlen(xforward) + 1);
    strtok(copy, ":");
    char *ip = strtok(0,"\r");
    while (*ip == ' ') ip++;      // Trim leading space
    jsn_add_string(params, "ip", ip);
  } else {
    jsn_add_string(params, "ip", get_env(argv, REMOTE_ADDR));
  }

Answer 1

fastest way?

If this code is executed AFTER the HTTP request PARSING G-WAN state then you could start searching for "X-Forwarded-For: " from the closest place (another HTTP header) instead of doing it from the start of the REQUEST.

There is no way to be significantly faster than xbuf_findstr(). String search methods are faster than others depending on the length of the input data, and this is not significant here.

"X-Forwarded-For: " was parsed by G-WAN in the past but as we have implemented a proxy feature in G-WAN, and since the "X-Forwarded-For: " header can be a fake, we removed it from the parser.