diff --git a/net/ip.hh b/net/ip.hh
index 3c8c139f1b..75f02b7d44 100644
--- a/net/ip.hh
+++ b/net/ip.hh
@@ -368,7 +368,7 @@ public:
     tcp<ipv4_traits>& get_tcp() { return *_tcp._tcp; }
     ipv4_udp& get_udp() { return _udp; }
     void register_l4(proto_type id, ip_protocol* handler);
-    net::hw_features hw_features() { return _netif->hw_features(); }
+    const net::hw_features& hw_features() const { return _netif->hw_features(); }
     static bool needs_frag(packet& p, ip_protocol_num proto_num, net::hw_features hw_features);
     void learn(ethernet_address l2, ipv4_address l3) {
         _arp.learn(l2, l3);
diff --git a/net/net.hh b/net/net.hh
index db7c954073..96cf20ff7b 100644
--- a/net/net.hh
+++ b/net/net.hh
@@ -119,7 +119,7 @@ private:
 public:
     explicit interface(std::shared_ptr<device> dev);
     ethernet_address hw_address() { return _hw_address; }
-    net::hw_features hw_features() { return _hw_features; }
+    const net::hw_features& hw_features() const { return _hw_features; }
     subscription<packet, ethernet_address> register_l3(eth_protocol_num proto_num,
             std::function<future<> (packet p, ethernet_address from)> next,
             std::function<bool (forward_hash&, packet&, size_t)> forward);
diff --git a/net/tcp.hh b/net/tcp.hh
index 91c0b9e061..648846a0cc 100644
--- a/net/tcp.hh
+++ b/net/tcp.hh
@@ -591,7 +591,7 @@ public:
     bool forward(forward_hash& out_hash_data, packet& p, size_t off);
     listener listen(uint16_t port, size_t queue_length = 100);
     future<connection> connect(socket_address sa);
-    net::hw_features hw_features() { return _inet._inet.hw_features(); }
+    const net::hw_features& hw_features() const { return _inet._inet.hw_features(); }
     future<> poll_tcb(ipaddr to, lw_shared_ptr<tcb> tcb);
 private:
     void send_packet_without_tcb(ipaddr from, ipaddr to, packet p);