1 files changed, 220 insertions, 0 deletions
diff --git a/src/expr/cmp.rs b/src/expr/cmp.rs
new file mode 100644
index 0000000..384f0b4
--- /dev/null
+++ b/src/expr/cmp.rs
@@ -0,0 +1,220 @@
+use super::{DeserializationError, Expression, Rule, ToSlice};
+use crate::sys::{self, libc};
+use std::{
+    borrow::Cow,
+    ffi::{c_void, CString},
+    os::raw::c_char,
+};
+
+/// Comparison operator.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum CmpOp {
+    /// Equals.
+    Eq,
+    /// Not equal.
+    Neq,
+    /// Less than.
+    Lt,
+    /// Less than, or equal.
+    Lte,
+    /// Greater than.
+    Gt,
+    /// Greater than, or equal.
+    Gte,
+}
+
+impl CmpOp {
+    /// Returns the corresponding `NFT_*` constant for this comparison operation.
+    pub fn to_raw(self) -> u32 {
+        use self::CmpOp::*;
+        match self {
+            Eq => libc::NFT_CMP_EQ as u32,
+            Neq => libc::NFT_CMP_NEQ as u32,
+            Lt => libc::NFT_CMP_LT as u32,
+            Lte => libc::NFT_CMP_LTE as u32,
+            Gt => libc::NFT_CMP_GT as u32,
+            Gte => libc::NFT_CMP_GTE as u32,
+        }
+    }
+
+    pub fn from_raw(val: u32) -> Result<Self, DeserializationError> {
+        use self::CmpOp::*;
+        match val as i32 {
+            libc::NFT_CMP_EQ => Ok(Eq),
+            libc::NFT_CMP_NEQ => Ok(Neq),
+            libc::NFT_CMP_LT => Ok(Lt),
+            libc::NFT_CMP_LTE => Ok(Lte),
+            libc::NFT_CMP_GT => Ok(Gt),
+            libc::NFT_CMP_GTE => Ok(Gte),
+            _ => Err(DeserializationError::InvalidValue),
+        }
+    }
+}
+
+/// Comparator expression. Allows comparing the content of the netfilter register with any value.
+#[derive(Debug, PartialEq)]
+pub struct Cmp<T> {
+    op: CmpOp,
+    data: T,
+}
+
+impl<T: ToSlice> Cmp<T> {
+    /// Returns a new comparison expression comparing the value loaded in the register with the
+    /// data in `data` using the comparison operator `op`.
+    pub fn new(op: CmpOp, data: T) -> Self {
+        Cmp { op, data }
+    }
+}
+
+impl<T: ToSlice> Expression for Cmp<T> {
+    fn get_raw_name() -> *const c_char {
+        b"cmp\0" as *const _ as *const c_char
+    }
+
+    fn to_expr(&self, _rule: &Rule) -> *mut sys::nftnl_expr {
+        unsafe {
+            let expr = try_alloc!(sys::nftnl_expr_alloc(Self::get_raw_name()));
+
+            let data = self.data.to_slice();
+            trace!("Creating a cmp expr comparing with data {:?}", data);
+
+            sys::nftnl_expr_set_u32(
+                expr,
+                sys::NFTNL_EXPR_CMP_SREG as u16,
+                libc::NFT_REG_1 as u32,
+            );
+            sys::nftnl_expr_set_u32(expr, sys::NFTNL_EXPR_CMP_OP as u16, self.op.to_raw());
+            sys::nftnl_expr_set(
+                expr,
+                sys::NFTNL_EXPR_CMP_DATA as u16,
+                data.as_ptr() as *const c_void,
+                data.len() as u32,
+            );
+
+            expr
+        }
+    }
+}
+
+impl<const N: usize> Expression for Cmp<[u8; N]> {
+    fn get_raw_name() -> *const c_char {
+        Cmp::<u8>::get_raw_name()
+    }
+
+    /// The raw data contained inside `Cmp` expressions can only be deserialized to
+    /// arrays of bytes, to ensure that the memory layout of retrieved data cannot be
+    /// violated. It is your responsibility to provide the correct length of the byte
+    /// data. If the data size is invalid, you will get the error
+    /// `DeserializationError::InvalidDataSize`.
+    ///
+    /// Example (warning, no error checking!):
+    /// ```rust
+    /// use std::ffi::CString;
+    /// use std::net::Ipv4Addr;
+    /// use std::rc::Rc;
+    ///
+    /// use rustables::{Chain, expr::{Cmp, CmpOp}, ProtoFamily, Rule, Table};
+    ///
+    /// let table = Rc::new(Table::new(&CString::new("mytable").unwrap(), ProtoFamily::Inet));
+    /// let chain = Rc::new(Chain::new(&CString::new("mychain").unwrap(), table));
+    /// let mut rule = Rule::new(chain);
+    /// rule.add_expr(&Cmp::new(CmpOp::Eq, 1337u16));
+    /// for expr in Rc::new(rule).get_exprs() {
+    ///     println!("{:?}", expr.decode_expr::<Cmp<[u8; 2]>>().unwrap());
+    /// }
+    /// ```
+    /// These limitations occur because casting bytes to any type of the same size
+    /// as the raw input would be *extremely* dangerous in terms of memory safety.
+    fn from_expr(expr: *const sys::nftnl_expr) -> Result<Self, DeserializationError> {
+        unsafe {
+            let ref_len = std::mem::size_of::<[u8; N]>() as u32;
+            let mut data_len = 0;
+            let data = sys::nftnl_expr_get(
+                expr,
+                sys::NFTNL_EXPR_CMP_DATA as u16,
+                &mut data_len as *mut u32,
+            );
+
+            if data.is_null() {
+                return Err(DeserializationError::NullPointer);
+            } else if data_len != ref_len {
+                return Err(DeserializationError::InvalidDataSize);
+            }
+
+            let data = *(data as *const [u8; N]);
+
+            let op = CmpOp::from_raw(sys::nftnl_expr_get_u32(expr, sys::NFTNL_EXPR_CMP_OP as u16))?;
+            Ok(Cmp { op, data })
+        }
+    }
+
+    // call to the other implementation to generate the expression
+    fn to_expr(&self, rule: &Rule) -> *mut sys::nftnl_expr {
+        Cmp {
+            data: &self.data as &[u8],
+            op: self.op,
+        }
+        .to_expr(rule)
+    }
+}
+
+#[macro_export(local_inner_macros)]
+macro_rules! nft_expr_cmp {
+    (@cmp_op ==) => {
+        $crate::expr::CmpOp::Eq
+    };
+    (@cmp_op !=) => {
+        $crate::expr::CmpOp::Neq
+    };
+    (@cmp_op <) => {
+        $crate::expr::CmpOp::Lt
+    };
+    (@cmp_op <=) => {
+        $crate::expr::CmpOp::Lte
+    };
+    (@cmp_op >) => {
+        $crate::expr::CmpOp::Gt
+    };
+    (@cmp_op >=) => {
+        $crate::expr::CmpOp::Gte
+    };
+    ($op:tt $data:expr) => {
+        $crate::expr::Cmp::new(nft_expr_cmp!(@cmp_op $op), $data)
+    };
+}
+
+/// Can be used to compare the value loaded by [`Meta::IifName`] and [`Meta::OifName`]. Please
+/// note that it is faster to check interface index than name.
+///
+/// [`Meta::IifName`]: enum.Meta.html#variant.IifName
+/// [`Meta::OifName`]: enum.Meta.html#variant.OifName
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub enum InterfaceName {
+    /// Interface name must be exactly the value of the `CString`.
+    Exact(CString),
+    /// Interface name must start with the value of the `CString`.
+    ///
+    /// `InterfaceName::StartingWith("eth")` will look like `eth*` when printed and match against
+    /// `eth0`, `eth1`, ..., `eth99` and so on.
+    StartingWith(CString),
+}
+
+impl ToSlice for InterfaceName {
+    fn to_slice(&self) -> Cow<'_, [u8]> {
+        let bytes = match *self {
+            InterfaceName::Exact(ref name) => name.as_bytes_with_nul(),
+            InterfaceName::StartingWith(ref name) => name.as_bytes(),
+        };
+        Cow::from(bytes)
+    }
+}
+
+impl<'a> ToSlice for &'a InterfaceName {
+    fn to_slice(&self) -> Cow<'_, [u8]> {
+        let bytes = match *self {
+            InterfaceName::Exact(ref name) => name.as_bytes_with_nul(),
+            InterfaceName::StartingWith(ref name) => name.as_bytes(),
+        };
+        Cow::from(bytes)
+    }
+}