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https://github.com/smoltcp-rs/smoltcp.git
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ipv6: use RFC6724 for selecting IPv6 src address
RFC6724 defines how the source address should be selected when given a destination address. Instead of selecting the first address in the list of interface addresses, the source address is selected following the standard.
This commit is contained in:
Thibaut Vandervelden
parent
45f9838ad9
commit
dd9eff7cf9
@ -176,7 +176,7 @@ fn main() {
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);
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icmp_repr.emit(&mut icmp_packet, &device_caps.checksum);
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}
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IpAddress::Ipv6(_) => {
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IpAddress::Ipv6(address) => {
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let (icmp_repr, mut icmp_packet) = send_icmp_ping!(
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Icmpv6Repr,
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Icmpv6Packet,
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@ -187,7 +187,10 @@ fn main() {
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remote_addr
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);
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icmp_repr.emit(
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&iface.ipv6_addr().unwrap().into_address(),
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&iface
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.get_source_address_ipv6(&address)
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.unwrap()
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.into_address(),
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&remote_addr,
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&mut icmp_packet,
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&device_caps.checksum,
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@ -217,11 +220,14 @@ fn main() {
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received
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);
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}
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IpAddress::Ipv6(_) => {
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IpAddress::Ipv6(address) => {
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let icmp_packet = Icmpv6Packet::new_checked(&payload).unwrap();
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let icmp_repr = Icmpv6Repr::parse(
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&remote_addr,
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&iface.ipv6_addr().unwrap().into_address(),
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&iface
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.get_source_address_ipv6(&address)
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.unwrap()
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.into_address(),
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&icmp_packet,
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&device_caps.checksum,
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)
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@ -464,6 +464,27 @@ impl Interface {
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self.inner.ipv6_addr()
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}
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/// Get an address from the interface that could be used as source address. For IPv4, this is
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/// the first IPv4 address from the list of addresses. For IPv6, the address is based on the
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/// destination address and uses RFC6724 for selecting the source address.
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pub fn get_source_address(&self, dst_addr: &IpAddress) -> Option<IpAddress> {
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self.inner.get_source_address(*dst_addr)
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}
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/// Get an address from the interface that could be used as source address. This is the first
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/// IPv4 address from the list of addresses in the interface.
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#[cfg(feature = "proto-ipv4")]
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pub fn get_source_address_ipv4(&self, dst_addr: &Ipv4Address) -> Option<Ipv4Address> {
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self.inner.get_source_address_ipv4(*dst_addr)
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}
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/// Get an address from the interface that could be used as source address. The selection is
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/// based on RFC6724.
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#[cfg(feature = "proto-ipv6")]
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pub fn get_source_address_ipv6(&self, dst_addr: &Ipv6Address) -> Option<Ipv6Address> {
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self.inner.get_source_address_ipv6(*dst_addr)
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}
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/// Update the IP addresses of the interface.
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///
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/// # Panics
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@ -927,7 +948,7 @@ impl InterfaceInner {
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}
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#[allow(unused)] // unused depending on which sockets are enabled
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pub(crate) fn get_source_address(&mut self, dst_addr: IpAddress) -> Option<IpAddress> {
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pub(crate) fn get_source_address(&self, dst_addr: IpAddress) -> Option<IpAddress> {
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match dst_addr {
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#[cfg(feature = "proto-ipv4")]
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IpAddress::Ipv4(addr) => self.get_source_address_ipv4(addr).map(|a| a.into()),
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@ -938,10 +959,7 @@ impl InterfaceInner {
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#[cfg(feature = "proto-ipv4")]
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#[allow(unused)]
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pub(crate) fn get_source_address_ipv4(
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&mut self,
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_dst_addr: Ipv4Address,
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) -> Option<Ipv4Address> {
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pub(crate) fn get_source_address_ipv4(&self, _dst_addr: Ipv4Address) -> Option<Ipv4Address> {
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for cidr in self.ip_addrs.iter() {
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#[allow(irrefutable_let_patterns)] // if only ipv4 is enabled
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if let IpCidr::Ipv4(cidr) = cidr {
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@ -953,17 +971,104 @@ impl InterfaceInner {
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#[cfg(feature = "proto-ipv6")]
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#[allow(unused)]
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pub(crate) fn get_source_address_ipv6(
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&mut self,
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_dst_addr: Ipv6Address,
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) -> Option<Ipv6Address> {
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for cidr in self.ip_addrs.iter() {
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#[allow(irrefutable_let_patterns)] // if only ipv6 is enabled
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if let IpCidr::Ipv6(cidr) = cidr {
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return Some(cidr.address());
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pub(crate) fn get_source_address_ipv6(&self, dst_addr: Ipv6Address) -> Option<Ipv6Address> {
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// RFC 6724 describes how to select the correct source address depending on the destination
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// address.
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// See RFC 6724 Section 4: Candidate source address
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fn is_candidate_source_address(dst_addr: &Ipv6Address, src_addr: &Ipv6Address) -> bool {
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// For all multicast and link-local destination addresses, the candidate address MUST
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// only be an address from the same link.
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if dst_addr.is_link_local() && !src_addr.is_link_local() {
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return false;
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}
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if dst_addr.is_multicast()
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&& matches!(dst_addr.scope(), Ipv6AddressScope::LinkLocal)
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&& src_addr.is_multicast()
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&& !matches!(src_addr.scope(), Ipv6AddressScope::LinkLocal)
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{
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return false;
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}
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// Loopback addresses and multicast address can not be in the candidate source address
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// list. Except when the destination multicast address has a link-local scope, then the
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// source address can also be link-local multicast.
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if src_addr.is_loopback() || src_addr.is_multicast() {
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return false;
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}
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true
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}
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// See RFC 6724 Section 2.2: Common Prefix Length
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fn common_prefix_length(dst_addr: &Ipv6Cidr, src_addr: &Ipv6Address) -> usize {
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let addr = dst_addr.address();
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let mut bits = 0;
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for (l, r) in addr.as_bytes().iter().zip(src_addr.as_bytes().iter()) {
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if l == r {
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bits += 8;
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} else {
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bits += (l ^ r).leading_zeros();
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break;
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}
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}
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bits = bits.min(dst_addr.prefix_len() as u32);
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bits as usize
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}
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// Get the first address that is a candidate address.
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let mut candidate = self
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.ip_addrs
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.iter()
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.filter_map(|a| match a {
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#[cfg(feature = "proto-ipv4")]
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IpCidr::Ipv4(_) => None,
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#[cfg(feature = "proto-ipv6")]
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IpCidr::Ipv6(a) => Some(a),
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})
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.find(|a| is_candidate_source_address(&dst_addr, &a.address()))
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.unwrap();
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for addr in self.ip_addrs.iter().filter_map(|a| match a {
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#[cfg(feature = "proto-ipv4")]
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IpCidr::Ipv4(_) => None,
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#[cfg(feature = "proto-ipv6")]
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IpCidr::Ipv6(a) => Some(a),
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}) {
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if !is_candidate_source_address(&dst_addr, &addr.address()) {
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continue;
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}
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// Rule 1: prefer the address that is the same as the output destination address.
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if candidate.address() != dst_addr && addr.address() == dst_addr {
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candidate = addr;
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}
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// Rule 2: prefer appropriate scope.
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if (candidate.address().scope() as u8) < (addr.address().scope() as u8) {
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if (candidate.address().scope() as u8) < (dst_addr.scope() as u8) {
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candidate = addr;
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}
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} else if (addr.address().scope() as u8) > (dst_addr.scope() as u8) {
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candidate = addr;
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}
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// Rule 3: avoid deprecated addresses (TODO)
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// Rule 4: prefer home addresses (TODO)
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// Rule 5: prefer outgoing interfaces (TODO)
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// Rule 5.5: prefer addresses in a prefix advertises by the next-hop (TODO).
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// Rule 6: prefer matching label (TODO)
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// Rule 7: prefer temporary addresses (TODO)
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// Rule 8: use longest matching prefix
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if common_prefix_length(candidate, &dst_addr) < common_prefix_length(addr, &dst_addr) {
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candidate = addr;
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}
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}
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None
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Some(candidate.address())
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}
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#[cfg(test)]
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@ -735,3 +735,95 @@ fn test_icmp_reply_size(#[case] medium: Medium) {
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))
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);
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}
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#[cfg(feature = "medium-ip")]
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#[test]
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fn get_source_address() {
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let (mut iface, _, _) = setup(Medium::Ip);
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const OWN_LINK_LOCAL_ADDR: Ipv6Address = Ipv6Address::new(0xfe80, 0, 0, 0, 0, 0, 0, 1);
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const OWN_UNIQUE_LOCAL_ADDR1: Ipv6Address = Ipv6Address::new(0xfd00, 0, 0, 201, 1, 1, 1, 2);
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const OWN_UNIQUE_LOCAL_ADDR2: Ipv6Address = Ipv6Address::new(0xfd01, 0, 0, 201, 1, 1, 1, 2);
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const OWN_GLOBAL_UNICAST_ADDR1: Ipv6Address =
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Ipv6Address::new(0x2001, 0x0db8, 0x0003, 0, 0, 0, 0, 1);
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// List of addresses of the interface:
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// fe80::1/64
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// fd00::201:1:1:1:2/64
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// fd01::201:1:1:1:2/64
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// 2001:db8:3::1/64
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// ::1/128
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// ::/128
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iface.update_ip_addrs(|addrs| {
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addrs.clear();
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addrs
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.push(IpCidr::Ipv6(Ipv6Cidr::new(OWN_LINK_LOCAL_ADDR, 64)))
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.unwrap();
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addrs
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.push(IpCidr::Ipv6(Ipv6Cidr::new(OWN_UNIQUE_LOCAL_ADDR1, 64)))
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.unwrap();
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addrs
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.push(IpCidr::Ipv6(Ipv6Cidr::new(OWN_UNIQUE_LOCAL_ADDR2, 64)))
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.unwrap();
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addrs
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.push(IpCidr::Ipv6(Ipv6Cidr::new(OWN_GLOBAL_UNICAST_ADDR1, 64)))
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.unwrap();
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// These should never be used:
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addrs
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.push(IpCidr::Ipv6(Ipv6Cidr::new(Ipv6Address::LOOPBACK, 128)))
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.unwrap();
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addrs
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.push(IpCidr::Ipv6(Ipv6Cidr::new(Ipv6Address::UNSPECIFIED, 128)))
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.unwrap();
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});
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// List of addresses we test:
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// fe80::42 -> fe80::1
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// fd00::201:1:1:1:1 -> fd00::201:1:1:1:2
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// fd01::201:1:1:1:1 -> fd01::201:1:1:1:2
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// fd02::201:1:1:1:1 -> fd00::201:1:1:1:2 (because first added in the list)
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// ff02::1 -> fe80::1 (same scope)
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// 2001:db8:3::2 -> 2001:db8:3::1
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// 2001:db9:3::2 -> 2001:db8:3::1
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const LINK_LOCAL_ADDR: Ipv6Address = Ipv6Address::new(0xfe80, 0, 0, 0, 0, 0, 0, 42);
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const UNIQUE_LOCAL_ADDR1: Ipv6Address = Ipv6Address::new(0xfd00, 0, 0, 201, 1, 1, 1, 1);
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const UNIQUE_LOCAL_ADDR2: Ipv6Address = Ipv6Address::new(0xfd01, 0, 0, 201, 1, 1, 1, 1);
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const UNIQUE_LOCAL_ADDR3: Ipv6Address = Ipv6Address::new(0xfd02, 0, 0, 201, 1, 1, 1, 1);
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const GLOBAL_UNICAST_ADDR1: Ipv6Address =
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Ipv6Address::new(0x2001, 0x0db8, 0x0003, 0, 0, 0, 0, 2);
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const GLOBAL_UNICAST_ADDR2: Ipv6Address =
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Ipv6Address::new(0x2001, 0x0db9, 0x0003, 0, 0, 0, 0, 2);
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assert_eq!(
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iface.inner.get_source_address_ipv6(LINK_LOCAL_ADDR),
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Some(OWN_LINK_LOCAL_ADDR)
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);
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assert_eq!(
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iface.inner.get_source_address_ipv6(UNIQUE_LOCAL_ADDR1),
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Some(OWN_UNIQUE_LOCAL_ADDR1)
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);
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assert_eq!(
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iface.inner.get_source_address_ipv6(UNIQUE_LOCAL_ADDR2),
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Some(OWN_UNIQUE_LOCAL_ADDR2)
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);
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assert_eq!(
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iface.inner.get_source_address_ipv6(UNIQUE_LOCAL_ADDR3),
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Some(OWN_UNIQUE_LOCAL_ADDR1)
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);
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assert_eq!(
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iface
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.inner
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.get_source_address_ipv6(Ipv6Address::LINK_LOCAL_ALL_NODES),
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Some(OWN_LINK_LOCAL_ADDR)
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);
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assert_eq!(
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iface.inner.get_source_address_ipv6(GLOBAL_UNICAST_ADDR1),
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Some(OWN_GLOBAL_UNICAST_ADDR1)
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);
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assert_eq!(
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iface.inner.get_source_address_ipv6(GLOBAL_UNICAST_ADDR2),
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Some(OWN_GLOBAL_UNICAST_ADDR1)
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);
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}
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