devtools/decodemsg: add --onion option for decoding onion errors.

This requires a tweak to generate-wire.py too, since it always called the
top-level routine 'print_message'.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

devtools/Makefile

@@ -1,4 +1,4 @@
-DEVTOOLS_SRC := devtools/gen_print_wire.c devtools/print_wire.c
+DEVTOOLS_SRC := devtools/gen_print_wire.c devtools/gen_print_onion_wire.c devtools/print_wire.c
 DEVTOOLS_OBJS := $(DEVTOOLS_SRC:.c=.o)
 DEVTOOLS_TOOL_SRC := devtools/bolt11-cli.c devtools/decodemsg.c devtools/onion.c
 DEVTOOLS_TOOL_OBJS := $(DEVTOOLS_TOOL_SRC:.c=.o)
@@ -23,6 +23,12 @@ devtools/gen_print_wire.h: $(WIRE_GEN) wire/gen_peer_wire_csv
 devtools/gen_print_wire.c: $(WIRE_GEN) wire/gen_peer_wire_csv
 	$(WIRE_GEN) --bolt --printwire ${@:.c=.h} wire_type < wire/gen_peer_wire_csv > $@
 
+devtools/gen_print_onion_wire.h: $(WIRE_GEN) wire/gen_onion_wire_csv
+	$(WIRE_GEN) --bolt --printwire --header $@ onion_type < wire/gen_onion_wire_csv > $@
+
+devtools/gen_print_onion_wire.c: $(WIRE_GEN) wire/gen_onion_wire_csv
+	$(WIRE_GEN) --bolt --printwire ${@:.c=.h} onion_type < wire/gen_onion_wire_csv > $@
+
 devtools/bolt11-cli: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o devtools/bolt11-cli.o
 
 devtools/decodemsg: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o devtools/decodemsg.o
@@ -31,8 +37,9 @@ devtools/onion.c: ccan/config.h
 
 devtools/onion: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o devtools/onion.o common/sphinx.o
 
-$(DEVTOOLS_OBJS) $(DEVTOOLS_TOOL_OBJS): wire/wire.h devtools/gen_print_wire.h
+$(DEVTOOLS_OBJS) $(DEVTOOLS_TOOL_OBJS): wire/wire.h devtools/gen_print_wire.h devtools/gen_print_onion_wire.h
 devtools/gen_print_wire.o: devtools/gen_print_wire.h wire/gen_peer_wire.h devtools/print_wire.h
+devtools/gen_print_onion_wire.o: devtools/gen_print_onion_wire.h devtools/print_wire.h
 
 # Make sure these depend on everything.
 ALL_PROGRAMS += devtools/bolt11-cli devtools/decodemsg devtools/onion

devtools/decodemsg.c

@@ -1,28 +1,36 @@
 #include <ccan/err/err.h>
+#include <ccan/opt/opt.h>
 #include <common/decode_short_channel_ids.h>
 #include <common/utils.h>
+#include <devtools/gen_print_onion_wire.h>
 #include <devtools/gen_print_wire.h>
 #include <stdio.h>
 
-static void usage(void)
-{
-	fprintf(stderr, "Usage: decodemsg <msg-in-hex>\n");
-	exit(1);
-}
-
 int main(int argc, char *argv[])
 {
 	const u8 *m;
+	bool onion = false;
 	setup_locale();
 
+	opt_register_noarg("--onion", opt_set_bool, &onion,
+			   "Decode an error message instead of a peer message");
+	opt_register_noarg("--help|-h", opt_usage_and_exit,
+			   "<hexmsg>"
+			   "Decode a lightning spec wire message from hex.",
+			   "Print this message.");
+
+	opt_parse(&argc, argv, opt_log_stderr_exit);
 	if (argc != 2)
-		usage();
+		errx(1, "Need a hex message");
 
-	/* Last arg is hex string */
+	/* Arg is hex string */
 	m = tal_hexdata(NULL, argv[1], strlen(argv[1]));
 	if (!m)
 		errx(1, "'%s' is not valid hex", argv[1]);
 
-	print_message(m);
+	if (onion)
+		printonion_type_message(m);
+	else
+		printwire_type_message(m);
 	return 0;
 }

tools/generate-wire.py

@@ -718,7 +718,7 @@ print_header_template = """/* This file was generated by generate-wire.py */
 #include <devtools/print_wire.h>
 {includes}
 
-void print_message(const u8 *msg);
+void print{enumname}_message(const u8 *msg);
 
 {func_decls}
 #endif /* LIGHTNING_{idem} */
@@ -732,7 +732,7 @@ print_template = """/* This file was generated by generate-wire.py */
 #include <common/utils.h>
 #include <stdio.h>
 
-void print_message(const u8 *msg)
+void print{enumname}_message(const u8 *msg)
 {{
 \tswitch ((enum {enumname})fromwire_peektype(msg)) {{
 \t{printcases}