Use own src address for ARP and NDISC Solicits

When looking up the destination link-layer address for a given destination address, we need to send an ARP or ICMPv6 Neighbor Solicitation if the destination link-layer address is not in the cache. When transmitting an ARP or ICMPv6 Neighbor Solicitation packet, use the source address of the interface instead of the source address of the packet that is tried to be sent. By using the source address of the interface, we are sure that a response will be received on the same interface.
smoltcp-rs · Sep 11, 2024 · c76f32f · c76f32f
1 parent 8e3ea5c
commit c76f32f
Show file tree

Hide file tree

Showing 3 changed files with 10 additions and 24 deletions.
diff --git a/src/iface/interface/mod.rs b/src/iface/interface/mod.rs
@@ -898,7 +898,6 @@ impl InterfaceInner {
     fn lookup_hardware_addr<Tx>(
         &mut self,
         tx_token: Tx,
-        src_addr: &IpAddress,
         dst_addr: &IpAddress,
         fragmenter: &mut Fragmenter,
     ) -> Result<(HardwareAddress, Tx), DispatchError>
@@ -966,11 +965,9 @@ impl InterfaceInner {
             _ => (), // XXX
         }
 
-        match (src_addr, dst_addr) {
+        match dst_addr {
             #[cfg(all(feature = "medium-ethernet", feature = "proto-ipv4"))]
-            (&IpAddress::Ipv4(src_addr), IpAddress::Ipv4(dst_addr))
-                if matches!(self.caps.medium, Medium::Ethernet) =>
-            {
+            IpAddress::Ipv4(dst_addr) if matches!(self.caps.medium, Medium::Ethernet) => {
                 net_debug!(
                     "address {} not in neighbor cache, sending ARP request",
                     dst_addr
@@ -980,7 +977,9 @@ impl InterfaceInner {
                 let arp_repr = ArpRepr::EthernetIpv4 {
                     operation: ArpOperation::Request,
                     source_hardware_addr: src_hardware_addr,
-                    source_protocol_addr: src_addr,
+                    source_protocol_addr: self
+                        .get_source_address_ipv4(&dst_addr)
+                        .ok_or(DispatchError::NoRoute)?,
                     target_hardware_addr: EthernetAddress::BROADCAST,
                     target_protocol_addr: dst_addr,
                 };
@@ -999,7 +998,7 @@ impl InterfaceInner {
             }
 
             #[cfg(feature = "proto-ipv6")]
-            (&IpAddress::Ipv6(src_addr), IpAddress::Ipv6(dst_addr)) => {
+            IpAddress::Ipv6(dst_addr) => {
                 net_debug!(
                     "address {} not in neighbor cache, sending Neighbor Solicitation",
                     dst_addr
@@ -1012,7 +1011,7 @@ impl InterfaceInner {
 
                 let packet = Packet::new_ipv6(
                     Ipv6Repr {
-                        src_addr,
+                        src_addr: self.get_source_address_ipv6(&dst_addr),
                         dst_addr: dst_addr.solicited_node(),
                         next_header: IpProtocol::Icmpv6,
                         payload_len: solicit.buffer_len(),
@@ -1059,12 +1058,8 @@ impl InterfaceInner {
 
         #[cfg(feature = "medium-ieee802154")]
         if matches!(self.caps.medium, Medium::Ieee802154) {
-            let (addr, tx_token) = self.lookup_hardware_addr(
-                tx_token,
-                &ip_repr.src_addr(),
-                &ip_repr.dst_addr(),
-                frag,
-            )?;
+            let (addr, tx_token) =
+                self.lookup_hardware_addr(tx_token, &ip_repr.dst_addr(), frag)?;
             let addr = addr.ieee802154_or_panic();
 
             self.dispatch_ieee802154(addr, tx_token, meta, packet, frag);
@@ -1091,12 +1086,7 @@ impl InterfaceInner {
         #[cfg(feature = "medium-ethernet")]
         let (dst_hardware_addr, mut tx_token) = match self.caps.medium {
             Medium::Ethernet => {
-                match self.lookup_hardware_addr(
-                    tx_token,
-                    &ip_repr.src_addr(),
-                    &ip_repr.dst_addr(),
-                    frag,
-                )? {
+                match self.lookup_hardware_addr(tx_token, &ip_repr.dst_addr(), frag)? {
                     (HardwareAddress::Ethernet(addr), tx_token) => (addr, tx_token),
                     (_, _) => unreachable!(),
                 }

diff --git a/src/iface/interface/tests/ipv4.rs b/src/iface/interface/tests/ipv4.rs
@@ -456,7 +456,6 @@ fn test_handle_valid_arp_request(#[case] medium: Medium) {
     assert_eq!(
         iface.inner.lookup_hardware_addr(
             MockTxToken,
-            &IpAddress::Ipv4(local_ip_addr),
             &IpAddress::Ipv4(remote_ip_addr),
             &mut iface.fragmenter,
         ),
@@ -505,7 +504,6 @@ fn test_handle_other_arp_request(#[case] medium: Medium) {
     assert_eq!(
         iface.inner.lookup_hardware_addr(
             MockTxToken,
-            &IpAddress::Ipv4(Ipv4Address([0x7f, 0x00, 0x00, 0x01])),
             &IpAddress::Ipv4(remote_ip_addr),
             &mut iface.fragmenter,
         ),
@@ -564,7 +562,6 @@ fn test_arp_flush_after_update_ip(#[case] medium: Medium) {
     assert_eq!(
         iface.inner.lookup_hardware_addr(
             MockTxToken,
-            &IpAddress::Ipv4(local_ip_addr),
             &IpAddress::Ipv4(remote_ip_addr),
             &mut iface.fragmenter,
         ),

diff --git a/src/iface/interface/tests/ipv6.rs b/src/iface/interface/tests/ipv6.rs
@@ -834,7 +834,6 @@ fn test_handle_valid_ndisc_request(#[case] medium: Medium) {
     assert_eq!(
         iface.inner.lookup_hardware_addr(
             MockTxToken,
-            &IpAddress::Ipv6(local_ip_addr),
             &IpAddress::Ipv6(remote_ip_addr),
             &mut iface.fragmenter,
         ),