Re #19 - Add the nat action to tc

src/rtnl/tc/constants.rs

@@ -93,3 +93,10 @@ pub const TCA_EGRESS_REDIR: i32 = 1; /* packet redirect to EGRESS */
 pub const TCA_EGRESS_MIRROR: i32 = 2; /* mirror packet to EGRESS */
 pub const TCA_INGRESS_REDIR: i32 = 3; /* packet redirect to INGRESS */
 pub const TCA_INGRESS_MIRROR: i32 = 4; /* mirror packet to INGRESS */
+
+/// NAT action attr
+pub const TCA_NAT_UNSPEC: u16 = 0;
+pub const TCA_NAT_PARMS: u16 = 1;
+pub const TCA_NAT_TM: u16 = 2;
+
+pub const TCA_NAT_FLAG_EGRESS: u32 = 1;

src/rtnl/tc/nlas/action/mod.rs

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
 
 pub mod mirred;
+pub mod nat;
 
 use anyhow::Context;
 use byteorder::{ByteOrder, NativeEndian};
@@ -160,6 +161,7 @@ impl nla::Nla for ActNla {
 #[non_exhaustive]
 pub enum ActOpt {
     Mirred(mirred::Nla),
+    Nat(nat::Nla),
     // Other options
     Other(DefaultNla),
 }
@@ -169,6 +171,7 @@ impl nla::Nla for ActOpt {
         use self::ActOpt::*;
         match self {
             Mirred(nla) => nla.value_len(),
+            Nat(nla) => nla.value_len(),
             Other(nla) => nla.value_len(),
         }
     }
@@ -177,6 +180,7 @@ impl nla::Nla for ActOpt {
         use self::ActOpt::*;
         match self {
             Mirred(nla) => nla.emit_value(buffer),
+            Nat(nla) => nla.emit_value(buffer),
             Other(nla) => nla.emit_value(buffer),
         }
     }
@@ -185,6 +189,7 @@ impl nla::Nla for ActOpt {
         use self::ActOpt::*;
         match self {
             Mirred(nla) => nla.kind(),
+            Nat(nla) => nla.kind(),
             Other(nla) => nla.kind(),
         }
     }
@@ -204,6 +209,9 @@ where
                 mirred::Nla::parse(buf)
                     .context("failed to parse mirred action")?,
             ),
+            nat::KIND => Self::Nat(
+                nat::Nla::parse(buf).context("failed to parse nat action")?,
+            ),
             _ => Self::Other(
                 DefaultNla::parse(buf)
                     .context("failed to parse action options")?,

src/rtnl/tc/nlas/action/nat.rs

@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: MIT
+
+/// Nat action
+///
+/// The nat action maps one IP prefix to another
+use std::net::Ipv4Addr;
+
+use netlink_packet_utils::{
+    nla::{self, DefaultNla, NlaBuffer},
+    traits::{Emitable, Parseable},
+    DecodeError,
+};
+
+use crate::tc::{constants::*, TC_GEN_BUF_LEN};
+
+pub const KIND: &str = "nat";
+pub const TC_NAT_BUF_LEN: usize = TC_GEN_BUF_LEN + 16;
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+#[non_exhaustive]
+pub enum Nla {
+    Unspec(Vec<u8>),
+    Tm(Vec<u8>),
+    Parms(TcNat),
+    Other(DefaultNla),
+}
+
+impl nla::Nla for Nla {
+    fn value_len(&self) -> usize {
+        use self::Nla::*;
+        match self {
+            Unspec(bytes) | Tm(bytes) => bytes.len(),
+            Parms(_) => TC_NAT_BUF_LEN,
+            Other(attr) => attr.value_len(),
+        }
+    }
+
+    fn emit_value(&self, buffer: &mut [u8]) {
+        use self::Nla::*;
+        match self {
+            Unspec(bytes) | Tm(bytes) => {
+                buffer.copy_from_slice(bytes.as_slice())
+            }
+            Parms(p) => p.emit(buffer),
+            Other(attr) => attr.emit_value(buffer),
+        }
+    }
+    fn kind(&self) -> u16 {
+        use self::Nla::*;
+        match self {
+            Unspec(_) => TCA_NAT_UNSPEC,
+            Tm(_) => TCA_NAT_TM,
+            Parms(_) => TCA_NAT_PARMS,
+            Other(nla) => nla.kind(),
+        }
+    }
+}
+
+impl<'a, T: AsRef<[u8]> + ?Sized> Parseable<NlaBuffer<&'a T>> for Nla {
+    fn parse(buf: &NlaBuffer<&'a T>) -> Result<Self, DecodeError> {
+        use self::Nla::*;
+        let payload = buf.value();
+        Ok(match buf.kind() {
+            TCA_NAT_UNSPEC => Unspec(payload.to_vec()),
+            TCA_NAT_TM => Tm(payload.to_vec()),
+            TCA_NAT_PARMS => {
+                Parms(TcNat::parse(&TcNatBuffer::new_checked(payload)?)?)
+            }
+            _ => Other(DefaultNla::parse(buf)?),
+        })
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Default)]
+#[non_exhaustive]
+pub struct TcNat {
+    pub index: u32,
+    pub capab: u32,
+    pub action: i32,
+    pub refcnt: i32,
+    pub bindcnt: i32,
+
+    pub old_addr: Vec<u8>,
+    pub new_addr: Vec<u8>,
+    pub mask: Vec<u8>,
+    pub flags: u32,
+}
+
+buffer!(TcNatBuffer(TC_NAT_BUF_LEN) {
+    index: (u32, 0..4),
+    capab: (u32, 4..8),
+    action: (i32, 8..12),
+    refcnt: (i32, 12..16),
+    bindcnt: (i32, 16..20),
+
+    old_addr: (slice, TC_GEN_BUF_LEN..(TC_GEN_BUF_LEN+4)),
+    new_addr: (slice, (TC_GEN_BUF_LEN +4)..(TC_GEN_BUF_LEN+8)),
+    mask: (slice, (TC_GEN_BUF_LEN +8)..(TC_GEN_BUF_LEN+12)),
+    flags: (u32, (TC_GEN_BUF_LEN+12)..TC_NAT_BUF_LEN),
+});
+
+impl TcNat {
+    pub fn set_new_addr(mut self, target: Ipv4Addr) -> Self {
+        self.new_addr = target.octets().to_vec();
+        self
+    }
+
+    pub fn set_old_addr(mut self, target: Ipv4Addr) -> Self {
+        self.old_addr = target.octets().to_vec();
+        self
+    }
+
+    pub fn set_prefix(mut self, prefix_len: usize) -> Self {
+        assert!(prefix_len <= 32);
+
+        let prefix: u32 = if prefix_len == 0 {
+            0x0
+        } else {
+            !((1 << (32 - prefix_len)) - 1)
+        };
+        self.mask = prefix.to_be_bytes().to_vec();
+
+        self
+    }
+
+    pub fn egress(mut self) -> Self {
+        self.flags = TCA_NAT_FLAG_EGRESS;
+        self
+    }
+}
+impl Emitable for TcNat {
+    fn buffer_len(&self) -> usize {
+        TC_NAT_BUF_LEN
+    }
+
+    fn emit(&self, buffer: &mut [u8]) {
+        let mut packet = TcNatBuffer::new(buffer);
+        packet.set_index(self.index);
+        packet.set_capab(self.capab);
+        packet.set_action(self.action);
+        packet.set_refcnt(self.refcnt);
+        packet.set_bindcnt(self.bindcnt);
+
+        packet.old_addr_mut().copy_from_slice(&self.old_addr[0..4]);
+        packet.new_addr_mut().copy_from_slice(&self.new_addr[0..4]);
+        packet.mask_mut().copy_from_slice(&self.mask[0..4]);
+        packet.set_flags(self.flags);
+    }
+}
+
+impl<'buf, T: AsRef<[u8]> + ?Sized> Parseable<TcNatBuffer<&'buf T>> for TcNat {
+    fn parse(buf: &TcNatBuffer<&'buf T>) -> Result<Self, DecodeError> {
+        Ok(Self {
+            index: buf.index(),
+            capab: buf.capab(),
+            action: buf.action(),
+            refcnt: buf.refcnt(),
+            bindcnt: buf.bindcnt(),
+            old_addr: buf.old_addr().to_vec(),
+            new_addr: buf.new_addr().to_vec(),
+            mask: buf.mask().to_vec(),
+            flags: buf.flags(),
+        })
+    }
+}