rpc/net: report per-peer last_inv_sequence

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 373169c0..ce4694d7 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -312,7 +312,7 @@ struct Peer {
         std::chrono::microseconds m_next_inv_send_time GUARDED_BY(m_tx_inventory_mutex){0};
         /** The mempool sequence num at which we sent the last `inv` message to this peer.
          *  Can relay txs with lower sequence numbers than this (see CTxMempool::info_for_relay). */
-        uint64_t m_last_inv_sequence GUARDED_BY(NetEventsInterface::g_msgproc_mutex){1};
+        uint64_t m_last_inv_sequence GUARDED_BY(m_tx_inventory_mutex){1};
 
         /** Minimum fee rate with which to filter transaction announcements to this node. See BIP133. */
         std::atomic<CAmount> m_fee_filter_received{0};
@@ -942,7 +942,7 @@ private:
 
     /** Determine whether or not a peer can request a transaction, and return it (or nullptr if not found or not allowed). */
     CTransactionRef FindTxForGetData(const Peer::TxRelay& tx_relay, const GenTxid& gtxid)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex, NetEventsInterface::g_msgproc_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex, !tx_relay.m_tx_inventory_mutex);
 
     void ProcessGetData(CNode& pfrom, Peer& peer, const std::atomic<bool>& interruptMsgProc)
         EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex, peer.m_getdata_requests_mutex, NetEventsInterface::g_msgproc_mutex)
@@ -1728,7 +1728,9 @@ bool PeerManagerImpl::GetNodeStateStats(NodeId nodeid, CNodeStateStats& stats) c
     if (auto tx_relay = peer->GetTxRelay(); tx_relay != nullptr) {
         stats.m_relay_txs = WITH_LOCK(tx_relay->m_bloom_filter_mutex, return tx_relay->m_relay_txs);
         stats.m_fee_filter_received = tx_relay->m_fee_filter_received.load();
-        stats.m_inv_to_send = WITH_LOCK(tx_relay->m_tx_inventory_mutex, return tx_relay->m_tx_inventory_to_send.size());
+        LOCK(tx_relay->m_tx_inventory_mutex);
+        stats.m_last_inv_seq = tx_relay->m_last_inv_sequence;
+        stats.m_inv_to_send = tx_relay->m_tx_inventory_to_send.size();
     } else {
         stats.m_relay_txs = false;
         stats.m_fee_filter_received = 0;
@@ -2364,8 +2366,8 @@ void PeerManagerImpl::ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv&
 CTransactionRef PeerManagerImpl::FindTxForGetData(const Peer::TxRelay& tx_relay, const GenTxid& gtxid)
 {
     auto txinfo{std::visit(
-        [&](const auto& id) EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex) {
-            return m_mempool.info_for_relay(id, tx_relay.m_last_inv_sequence);
+        [&](const auto& id) {
+            return m_mempool.info_for_relay(id, WITH_LOCK(tx_relay.m_tx_inventory_mutex, return tx_relay.m_last_inv_sequence));
         },
         gtxid)};
 
diff --git a/src/net_processing.h b/src/net_processing.h
index ee12bd08..6eb4a5e1 100644
--- a/src/net_processing.h
+++ b/src/net_processing.h
@@ -55,6 +55,7 @@ struct CNodeStateStats {
     std::vector<int> vHeightInFlight;
     bool m_relay_txs;
     int m_inv_to_send = 0;
+    uint64_t m_last_inv_seq{0};
     CAmount m_fee_filter_received;
     uint64_t m_addr_processed = 0;
     uint64_t m_addr_rate_limited = 0;
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index e5b9880a..ba74283d 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -142,6 +142,7 @@ static RPCHelpMan getpeerinfo()
                         {RPCResult::Type::STR, "SERVICE_NAME", "the service name if it is recognised"}
                     }},
                     {RPCResult::Type::BOOL, "relaytxes", "Whether we relay transactions to this peer"},
+                    {RPCResult::Type::NUM, "last_inv_sequence", "Mempool sequence number of this peer's last INV"},
                     {RPCResult::Type::NUM, "inv_to_send", "How many txs we have queued to announce to this peer"},
                     {RPCResult::Type::NUM_TIME, "lastsend", "The " + UNIX_EPOCH_TIME + " of the last send"},
                     {RPCResult::Type::NUM_TIME, "lastrecv", "The " + UNIX_EPOCH_TIME + " of the last receive"},
@@ -239,6 +240,7 @@ static RPCHelpMan getpeerinfo()
         obj.pushKV("services", strprintf("%016x", services));
         obj.pushKV("servicesnames", GetServicesNames(services));
         obj.pushKV("relaytxes", statestats.m_relay_txs);
+        obj.pushKV("last_inv_sequence", statestats.m_last_inv_seq);
         obj.pushKV("inv_to_send", statestats.m_inv_to_send);
         obj.pushKV("lastsend", count_seconds(stats.m_last_send));
         obj.pushKV("lastrecv", count_seconds(stats.m_last_recv));
diff --git a/test/functional/rpc_net.py b/test/functional/rpc_net.py
index f52d59d7..aeaf20c2 100755
--- a/test/functional/rpc_net.py
+++ b/test/functional/rpc_net.py
@@ -167,6 +167,7 @@ class NetTest(BitcoinTestFramework):
                 "presynced_headers": -1,
                 "relaytxes": False,
                 "inv_to_send": 0,
+                "last_inv_sequence": 0,
                 "services": "0000000000000000",
                 "servicesnames": [],
                 "session_id": "" if not self.options.v2transport else no_version_peer.v2_state.peer['session_id'].hex(),