From 4718ee076c1ae001d2cb511c86341ae1a4025d3d Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 31 Mar 2022 19:40:50 +1030
Subject: [PATCH] lightningd: metadata received support (log and decline).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 common/onion.c          |  7 +++++++
 common/onion.h          |  1 +
 lightningd/peer_htlcs.c | 31 +++++++++++++++++++++++++++++--
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/common/onion.c b/common/onion.c
index 5fdcf7579..5f3f71bc4 100644
--- a/common/onion.c
+++ b/common/onion.c
@@ -241,6 +241,7 @@ struct onion_payload *onion_decode(const tal_t *ctx,
 		p->amt_to_forward = fromwire_amount_msat(&cursor, &max);
 		p->outgoing_cltv = fromwire_u32(&cursor, &max);
 		p->payment_secret = NULL;
+		p->payment_metadata = NULL;
 		p->blinding = NULL;
 		/* We can't handle blinding with a legacy payload */
 		if (blinding)
@@ -365,6 +366,12 @@ struct onion_payload *onion_decode(const tal_t *ctx,
 		*p->total_msat
 			= amount_msat(tlv->payment_data->total_msat);
 	}
+	if (tlv->payment_metadata)
+		p->payment_metadata
+			= tal_dup_talarr(p, u8, tlv->payment_metadata);
+	else
+		p->payment_metadata = NULL;
+
 	p->tlv = tal_steal(p, tlv);
 	return p;
 
diff --git a/common/onion.h b/common/onion.h
index 6f3045faf..828a6735d 100644
--- a/common/onion.h
+++ b/common/onion.h
@@ -19,6 +19,7 @@ struct onion_payload {
 	struct amount_msat *total_msat;
 	struct short_channel_id *forward_channel;
 	struct secret *payment_secret;
+	u8 *payment_metadata;
 
 	/* If blinding is set, blinding_ss is the shared secret.*/
 	struct pubkey *blinding;
diff --git a/lightningd/peer_htlcs.c b/lightningd/peer_htlcs.c
index 0f506c3b9..763ce23a4 100644
--- a/lightningd/peer_htlcs.c
+++ b/lightningd/peer_htlcs.c
@@ -363,7 +363,8 @@ static void handle_localpay(struct htlc_in *hin,
 			    struct amount_msat amt_to_forward,
 			    u32 outgoing_cltv_value,
 			    struct amount_msat total_msat,
-			    const struct secret *payment_secret)
+			    const struct secret *payment_secret,
+			    const u8 *payment_metadata)
 {
 	const u8 *failmsg;
 	struct lightningd *ld = hin->key.channel->peer->ld;
@@ -424,6 +425,27 @@ static void handle_localpay(struct htlc_in *hin,
 		goto fail;
 	}
 
+	/* We don't expect payment_metadata; reject here */
+	if (payment_metadata) {
+		log_debug(hin->key.channel->log,
+			  "Unexpected payment_metadata %s",
+			  tal_hex(tmpctx, payment_metadata));
+		/* BOLT #4:
+		 * 1. type: PERM|22 (`invalid_onion_payload`)
+		 * 2. data:
+		 *    * [`bigsize`:`type`]
+		 *    * [`u16`:`offset`]
+		 *
+		 * The decrypted onion per-hop payload was not understood by the processing node
+		 * or is incomplete. If the failure can be narrowed down to a specific tlv type in
+		 * the payload, the erring node may include that `type` and its byte `offset` in
+		 * the decrypted byte stream.
+		 */
+		failmsg = towire_invalid_onion_payload(NULL, TLV_TLV_PAYLOAD_PAYMENT_METADATA,
+						       /* FIXME: offset? */ 0);
+		goto fail;
+	}
+
 	htlc_set_add(ld, hin, total_msat, payment_secret);
 	return;
 
@@ -1033,6 +1055,10 @@ static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
 			json_add_secret(s, "payment_secret",
 					p->payload->payment_secret);
 		}
+		if (p->payload->payment_metadata) {
+			json_add_hex_talarr(s, "payment_metadata",
+					    p->payload->payment_metadata);
+		}
 	}
 	json_add_hex_talarr(s, "next_onion", p->next_onion);
 	json_add_secret(s, "shared_secret", hin->shared_secret);
@@ -1082,7 +1108,8 @@ htlc_accepted_hook_final(struct htlc_accepted_hook_payload *request STEALS)
 				request->payload->amt_to_forward,
 				request->payload->outgoing_cltv,
 				*request->payload->total_msat,
-				request->payload->payment_secret);
+				request->payload->payment_secret,
+				request->payload->payment_metadata);
 
 	tal_free(request);
 }