Chore/refactor: get rid of Host struct

We don't really need this Host struct anymore, it's pretty much a
duplicate of the Rust Hostent version at this point. Getting rid of
it, moving the serialization procedure to the Hostent structure.

src/ffi.rs

@@ -76,6 +76,15 @@ mod glibcffi {
     }
 }
 
+/// This structure is the Rust counterpart of the `libc::hostent` C
+/// function the Libc hostent struct.
+///
+/// It's mostly used to perform the gethostbyaddr and gethostbyname
+/// operations.
+///
+/// This struct can be serialized to the wire through the
+/// `serialize` function or retrieved from the C boundary using the
+/// TryFrom `libc:hostent` trait.
 #[derive(Clone, Debug)]
 pub struct Hostent {
     pub name: String,

src/handlers.rs

@@ -27,7 +27,7 @@ use nix::unistd::{getgrouplist, Gid, Group, Uid, User};
 use slog::{debug, error, Logger};
 use std::mem::size_of;
 
-use crate::ffi::{gethostbyname2_r, gethostbyaddr_r, LibcIp};
+use crate::ffi::{gethostbyname2_r, gethostbyaddr_r, LibcIp, Hostent};
 use crate::protocol::{AiResponse, AiResponseHeader};
 
 use super::config::Config;
@@ -180,11 +180,7 @@ pub fn handle_request(
                 Ok(hostent) => hostent,
                 Err(e) => bail!("error during lookup: {:?}", e)
             };
-            let host = Host {
-                addresses: hostent.addr_list,
-                hostname: hostent.name
-            };
-            host.serialize()
+            hostent.serialize()
         }
         RequestType::GETHOSTBYADDRv6 => {
             let key = request.key;
@@ -197,11 +193,7 @@ pub fn handle_request(
                 Ok(hostent) => hostent,
                 Err(e) => bail!("error during lookup: {:?}", e)
             };
-            let host = Host {
-                addresses: hostent.addr_list,
-                hostname: hostent.name
-            };
-            host.serialize()
+            hostent.serialize()
         }
 
         RequestType::GETHOSTBYNAME => {
@@ -210,11 +202,7 @@ pub fn handle_request(
                 Ok(hostent) => hostent,
                 Err(e) => bail!("error during lookup: {:?}", e)
             };
-            let host = Host {
-                addresses: hostent.addr_list,
-                hostname: hostent.name
-            };
-            host.serialize()
+            hostent.serialize()
         }
 
         RequestType::GETHOSTBYNAMEv6 => {
@@ -224,11 +212,7 @@ pub fn handle_request(
                 Ok(hostent) => hostent,
                 Err(e) => bail!("error during lookup: {:?}", e)
             };
-            let host = Host {
-                addresses: hostent.addr_list,
-                hostname: hostent.name
-            };
-            host.serialize()
+            hostent.serialize()
         }
 
         // These will normally send an FD pointing to the internal cache structure,
@@ -354,13 +338,7 @@ fn serialize_initgroups(groups: Vec<Gid>) -> Result<Vec<u8>> {
     Ok(result)
 }
 
-pub struct Host {
-    pub addresses: Vec<std::net::IpAddr>,
-    // aliases is unused so far
-    pub hostname: String,
-}
-
-impl Host {
+impl Hostent {
     fn serialize(&self) -> Result<Vec<u8>> {
         // Loop over all addresses.
         // Serialize them into a slice, which is used later in the payload.
@@ -369,7 +347,7 @@ impl Host {
         let mut num_v6 = 0;
         let mut buf_addrs = vec![];
 
-        for address in self.addresses.iter() {
+        for address in self.addr_list.iter() {
             match address {
                 IpAddr::V4(ip4) => {
                     num_v4 += 1;
@@ -394,7 +372,7 @@ impl Host {
         let num_addrs = num_v4 + num_v6;
         let has_addrs = num_addrs > 0;
 
-        let hostname_c_string_bytes = CString::new(self.hostname.clone())?.into_bytes_with_nul();
+        let hostname_c_string_bytes = CString::new(self.name.clone())?.into_bytes_with_nul();
         let hostname_c_string_len = if has_addrs {
             hostname_c_string_bytes.len() as i32
         } else {
@@ -522,6 +500,8 @@ fn serialize_address_info(resp: &AiResponse) -> Result<Vec<u8>> {
 
 #[cfg(test)]
 mod test {
+    use nix::libc::{AF_INET, AF_INET6};
+
     use super::super::config::Config;
     use std::net::{Ipv4Addr, Ipv6Addr};
 
@@ -623,9 +603,11 @@ mod test {
             key: &[127, 0, 0, 1],
         };
 
-        let expected = (Host {
-                addresses: vec![IpAddr::from(Ipv4Addr::new(127, 0, 0, 1))],
-                hostname: "localhost".to_string(),
+        let expected = (Hostent {
+            addr_list: vec![IpAddr::from(Ipv4Addr::new(127, 0, 0, 1))],
+            name: "localhost".to_string(),
+            addr_type: AF_INET,
+            aliases: Vec::new()
         }).serialize().expect("must succeed");
 
         let output = handle_request(&test_logger(), &Config::default(), &request)
@@ -653,9 +635,12 @@ mod test {
             key: &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
         };
 
-        let expected = (Host {
-                addresses: vec![IpAddr::from(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1))],
-                hostname: "localhost".to_string(),
+        let expected = (Hostent {
+            addr_list: vec![IpAddr::from(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1))],
+            name: "localhost".to_string(),
+            addr_type: AF_INET6,
+            aliases: Vec::new()
+
             }).serialize().expect("must succeed");
 
         let output = handle_request(&test_logger(), &Config::default(), &request)