-extern char *client_referrer(const struct parsers *v, char *s, struct client_state *csp);
-extern char *client_uagent(const struct parsers *v, char *s, struct client_state *csp);
-extern char *client_ua(const struct parsers *v, char *s, struct client_state *csp);
-extern char *client_from(const struct parsers *v, char *s, struct client_state *csp);
-extern char *client_send_cookie(const struct parsers *v, char *s, struct client_state *csp);
-extern char *client_x_forwarded(const struct parsers *v, char *s, struct client_state *csp);
+extern char *client_referrer(const struct parsers *v, const char *s, struct client_state *csp);
+extern char *client_uagent(const struct parsers *v, const char *s, struct client_state *csp);
+extern char *client_ua(const struct parsers *v, const char *s, struct client_state *csp);
+extern char *client_from(const struct parsers *v, const char *s, struct client_state *csp);
+extern char *client_send_cookie(const struct parsers *v, const char *s, struct client_state *csp);
+extern char *client_x_forwarded(const struct parsers *v, const char *s, struct client_state *csp);