Add VCLI_Overflow() so we can stop rendering bans when the CLI

output buffer is full.

bin/varnishd/cache/cache_ban.c

@@ -1071,6 +1071,8 @@ ccf_ban_list(struct cli *cli, const char * const *av, void *priv)
 		    b->flags & BAN_F_GONE ? "G" : " ");
 		ban_render(cli, b->spec);
 		VCLI_Out(cli, "\n");
+		if (VCLI_Overflow(cli))
+			break;
 		if (cache_param->diag_bitmap & 0x80000) {
 			Lck_Lock(&ban_mtx);
 			struct objcore *oc;

include/vcli_priv.h

@@ -52,6 +52,7 @@ struct cli_proto {
 };
 
 /* The implementation must provide these functions */
+int VCLI_Overflow(struct cli *cli);
 void VCLI_Out(struct cli *cli, const char *fmt, ...);
 void VCLI_Quote(struct cli *cli, const char *str);
 void VCLI_SetResult(struct cli *cli, unsigned r);

lib/libvarnish/cli_common.c

@@ -69,6 +69,17 @@ VCLI_Out(struct cli *cli, const char *fmt, ...)
 	va_end(ap);
 }
 
+/*lint -e{818} cli could be const */
+int
+VCLI_Overflow(struct cli *cli)
+{
+	CHECK_OBJ_NOTNULL(cli, CLI_MAGIC);
+	if (cli->result == CLIS_TRUNCATED ||
+	    VSB_len(cli->sb) >= *cli->limit)
+		return (1);
+	return (0);
+}
+
 /*lint -e{818} cli could be const */
 void
 VCLI_Quote(struct cli *cli, const char *s)