tagline: bump max length 260 -> 400, replace magic number with named constant

inc/tagline.h

@@ -60,6 +60,43 @@ typedef	Tagline_V10_32		Tagline32;
 #define	TAGLINE_DB_CURRENT_VERSION		10
 #define TAGLINE_DB_SUPPORTED_VERSION	"10"
 
+/*
+ * TAGLINE_MAX_LEN -- hard cap on tagline text length, in bytes.
+ *
+ * This is not an arbitrary knob. The tightest constraint is not storage
+ * or the inbound PRIVMSG the operator sends to OperServ (servers use a
+ * nick-only prefix when propagating client traffic, per RFC 1459 s.2.3
+ * and bahamut convention, which leaves ample room). It is the *outbound*
+ * broadcast produced by send_globops() in handle_tagline() and
+ * tagline_show(), which bahamut turns into a NOTICE to every +g operator
+ * (see src/send.c:send_globops in bahamut):
+ *
+ *     :<server> NOTICE <destnick> :*** Global -- \2<caller>\2
+ *     (through \2<oper>\2) added the following tagline: <text>\r\n
+ *
+ * The IRC protocol caps a single line at 512 bytes including the
+ * trailing CR-LF (RFC 1459 s.2.3.1). Worst-case byte budget:
+ *
+ *     `:<server>` (HOSTMAX=63) + ` NOTICE ` (8) + `<destnick>`
+ *     (NICKMAX=32) + ` :*** Global -- ` (16) + bold markers + `<caller>`
+ *     (NICKMAX=32) + ` (through ` (10) + bold markers + `<oper>`
+ *     (NICKMAX=32) + `) added the following tagline: ` (31) + <text>
+ *     + `\r\n` (2) ~= 230 + text
+ *
+ * So the theoretical worst case caps text at ~280, though realistic
+ * Azzurra params (server name ~21, operator nicks ~8-12) leave comfortable
+ * headroom. 350 keeps us well clear of truncation across both realistic
+ * and near-worst-case combinations without pushing the limit.
+ *
+ * Before raising this value, re-derive both envelopes (services-side
+ * send_globops() and bahamut's send_globops() NOTICE wrapper) against
+ * every call site that embeds a tagline. Blind increases cause silent
+ * truncation at the receiving server with no feedback to the originating
+ * operator -- the stored tagline is fine, but the GLOBOPS confirmation
+ * message seen by +g opers gets its tail cut.
+ */
+#define TAGLINE_MAX_LEN				350
+
 
 /*********************************************************
  * Global variables                                      *

src/tagline.c

@@ -327,9 +327,9 @@ void handle_tagline(CSTR source, User *callerUser, ServiceCommandData *data) {
 			return;
 		}
 
-		if ((len = str_len(text)) > 260) {
+		if ((len = str_len(text)) > TAGLINE_MAX_LEN) {
 
-			send_notice_to_user(s_OperServ, callerUser, "The maximum length for a tagline is 260 characters. Your tagline has %d.", len);
+			send_notice_to_user(s_OperServ, callerUser, "The maximum length for a tagline is %d characters. Your tagline has %d.", TAGLINE_MAX_LEN, len);
 			return;
 		}
 
@@ -417,7 +417,7 @@ void handle_tagline(CSTR source, User *callerUser, ServiceCommandData *data) {
 			return;
 		}
 
-		if (str_len(text) > 260) {
+		if (str_len(text) > TAGLINE_MAX_LEN) {
 
 			send_notice_to_user(s_OperServ, callerUser, "Tagline not found.");
 			return;