common/wire_error: helpers to create/parse WIRE_ERROR messages.

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

common/Makefile

@@ -32,6 +32,7 @@ COMMON_SRC :=					\
 	common/utils.c				\
 	common/utxo.c				\
 	common/version.c			\
+	common/wire_error.c			\
 	common/withdraw_tx.c
 
 COMMON_HEADERS_NOGEN := $(COMMON_SRC:.c=.h) common/overflows.h common/htlc.h

common/wire_error.c

@@ -0,0 +1,93 @@
+#include <ccan/mem/mem.h>
+#include <ccan/tal/str/str.h>
+#include <common/type_to_string.h>
+#include <common/utils.h>
+#include <common/wire_error.h>
+#include <wire/gen_peer_wire.h>
+
+u8 *towire_errorfmtv(const tal_t *ctx,
+		     const struct channel_id *channel,
+		     const char *fmt,
+		     va_list ap)
+{
+	/* BOLT #1:
+	 *
+	 * The channel is referred to by `channel_id` unless `channel_id` is
+	 * zero (ie. all bytes zero), in which case it refers to all
+	 * channels. */
+	static const struct channel_id all_channels;
+	char *estr;
+	u8 *msg;
+
+	estr = tal_vfmt(ctx, fmt, ap);
+	/* We need tal_len to work, so we use copy. */
+	msg = towire_error(ctx, channel ? channel : &all_channels,
+			   (u8 *)tal_dup_arr(estr, char, estr, strlen(estr), 0));
+	tal_free(estr);
+	va_end(ap);
+
+	return msg;
+}
+
+u8 *towire_errorfmt(const tal_t *ctx,
+		    const struct channel_id *channel,
+		    const char *fmt, ...)
+{
+	va_list ap;
+	u8 *msg;
+
+	va_start(ap, fmt);
+	msg = towire_errorfmtv(ctx, channel, fmt, ap);
+	va_end(ap);
+
+	return msg;
+}
+
+bool is_all_channels(const struct channel_id *channel_id)
+{
+	/* BOLT #1:
+	 *
+	 * A node receiving `error` MUST fail the channel referred to by the
+	 * message, or if `channel_id` is zero, it MUST fail all channels and
+	 * MUST close the connection.  If no existing channel is referred to
+	 * by the message, the receiver MUST ignore the message.
+	 */
+	return memeqzero(channel_id, sizeof(*channel_id));
+}
+
+char *sanitize_error(const tal_t *ctx, const u8 *errmsg,
+		     struct channel_id *channel_id)
+{
+	struct channel_id dummy;
+	u8 *data;
+	size_t i;
+
+	if (!channel_id)
+		channel_id = &dummy;
+
+	if (!fromwire_error(ctx, errmsg, NULL, channel_id, &data))
+		return tal_fmt(ctx, "Invalid ERROR message '%s'",
+			       tal_hex(ctx, errmsg));
+
+	/* BOLT #1:
+	 *
+	 * A receiving node SHOULD only print out `data` verbatim if the
+	 * string is composed solely of printable ASCII characters.  For
+	 * reference, the printable character set includes byte values 32
+	 * through 127 inclusive.
+	 */
+	for (i = 0; i < tal_len(data); i++) {
+		if (data[i] < 32 || data[i] > 127) {
+			/* Convert to hex, minus NUL term */
+			data = (u8 *)tal_hex(ctx, data);
+			tal_resize(&data, tal_len(data)-1);
+			break;
+		}
+	}
+
+	return tal_fmt(ctx, "channel %s: %.*s",
+		       is_all_channels(channel_id)
+		       ? "ALL"
+		       : type_to_string(ctx, struct channel_id, channel_id),
+		       (int)tal_len(data), (char *)data);
+}

common/wire_error.h

@@ -0,0 +1,50 @@
+#ifndef LIGHTNING_COMMON_WIRE_ERROR_H
+#define LIGHTNING_COMMON_WIRE_ERROR_H
+#include "config.h"
+#include <ccan/compiler/compiler.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+#include <stdarg.h>
+
+struct channel_id;
+
+/**
+ * towire_errorfmt - helper to turn string into WIRE_ERROR.
+ *
+ * @ctx: context to allocate from
+ * @channel: specific channel to complain about, or NULL for all.
+ * @fmt: format for error.
+ */
+u8 *towire_errorfmt(const tal_t *ctx,
+		    const struct channel_id *channel,
+		    const char *fmt, ...) PRINTF_FMT(3,4);
+
+/**
+ * towire_errorfmtv - helper to turn string into WIRE_ERROR.
+ *
+ * @ctx: context to allocate from
+ * @channel: specific channel to complain about, or NULL for all.
+ * @fmt: format for error.
+ * @ap: accumulated varargs.
+ */
+u8 *towire_errorfmtv(const tal_t *ctx,
+		     const struct channel_id *channel,
+		     const char *fmt,
+		     va_list ap);
+
+/**
+ * is_all_channels - True if channel_id is all zeroes.
+ */
+bool is_all_channels(const struct channel_id *channel_id);
+
+/**
+ * sanitize_error - extract and sanitize contents of WIRE_ERROR.
+ *
+ * @ctx: context to allocate from
+ * @errmsg: the wire_error
+ * @channel: (out) channel it's referrring to, or NULL if don't care.
+ */
+char *sanitize_error(const tal_t *ctx, const u8 *errmsg,
+		     struct channel_id *channel_id);
+
+#endif /* LIGHTNING_COMMON_WIRE_ERROR_H */