Support for captive URLs (#31)

Author: ivmarkov

edge-dhcp/src/io/client.rs

@@ -16,18 +16,21 @@ use crate::{Options, Packet};
 
 /// Represents the additional network-related information that might be returned by the DHCP server.
 #[derive(Debug, Clone)]
-pub struct NetworkInfo {
+#[non_exhaustive]
+pub struct NetworkInfo<'a> {
     pub gateway: Option<Ipv4Addr>,
     pub subnet: Option<Ipv4Addr>,
     pub dns1: Option<Ipv4Addr>,
     pub dns2: Option<Ipv4Addr>,
+    pub captive_url: Option<&'a str>,
 }
 
 /// Represents a DHCP IP lease.
 ///
 /// This structure has a set of asynchronous methods that can utilize a supplied DHCP client instance and UDP socket to
 /// transparently implement all aspects of negotiating an IP with the DHCP server and then keeping the lease of that IP up to date.
 #[derive(Debug, Clone)]
+#[non_exhaustive]
 pub struct Lease {
     pub ip: Ipv4Addr,
     pub server_ip: Ipv4Addr,
@@ -40,46 +43,57 @@ impl Lease {
     /// This is done by utilizing the supplied DHCP client instance and UDP socket.
     ///
     /// Note that the supplied UDP socket should be capable of sending and receiving broadcast UDP packets.
-    pub async fn new<T, S>(
+    pub async fn new<'a, T, S>(
         client: &mut dhcp::client::Client<T>,
         socket: &mut S,
-        buf: &mut [u8],
-    ) -> Result<(Self, NetworkInfo), Error<S::Error>>
+        buf: &'a mut [u8],
+    ) -> Result<(Self, NetworkInfo<'a>), Error<S::Error>>
     where
         T: RngCore,
         S: UdpReceive + UdpSend,
     {
         loop {
             let offer = Self::discover(client, socket, buf, Duration::from_secs(3)).await?;
+            let server_ip = offer.server_ip.unwrap();
+            let ip = offer.ip;
 
             let now = Instant::now();
 
-            if let Some(settings) = Self::request(
-                client,
-                socket,
-                buf,
-                offer.server_ip.unwrap(),
-                offer.ip,
-                true,
-                Duration::from_secs(3),
-                3,
-            )
-            .await?
             {
-                break Ok((
-                    Self {
-                        ip: settings.ip,
-                        server_ip: settings.server_ip.unwrap(),
-                        duration: Duration::from_secs(settings.lease_time_secs.unwrap_or(7200) as _),
-                        acquired: now,
-                    },
-                    NetworkInfo {
-                        gateway: settings.gateway,
-                        subnet: settings.subnet,
-                        dns1: settings.dns1,
-                        dns2: settings.dns2,
-                    },
-                ));
+                // Nasty but necessary to avoid Rust's borrow checker not dealing
+                // with the non-lexical lifetimes involved here
+                let buf = unsafe { Self::unsafe_reborrow(buf) };
+
+                if let Some(settings) = Self::request(
+                    client,
+                    socket,
+                    buf,
+                    server_ip,
+                    ip,
+                    true,
+                    Duration::from_secs(3),
+                    3,
+                )
+                .await?
+                {
+                    break Ok((
+                        Self {
+                            ip: settings.ip,
+                            server_ip: settings.server_ip.unwrap(),
+                            duration: Duration::from_secs(
+                                settings.lease_time_secs.unwrap_or(7200) as _
+                            ),
+                            acquired: now,
+                        },
+                        NetworkInfo {
+                            gateway: settings.gateway,
+                            subnet: settings.subnet,
+                            dns1: settings.dns1,
+                            dns2: settings.dns2,
+                            captive_url: settings.captive_url,
+                        },
+                    ));
+                }
             }
         }
     }
@@ -173,12 +187,12 @@ impl Lease {
         Ok(())
     }
 
-    async fn discover<T, S>(
+    async fn discover<'a, T, S>(
         client: &mut dhcp::client::Client<T>,
         socket: &mut S,
-        buf: &mut [u8],
+        buf: &'a mut [u8],
         timeout: Duration,
-    ) -> Result<Settings, Error<S::Error>>
+    ) -> Result<Settings<'a>, Error<S::Error>>
     where
         T: RngCore,
         S: UdpReceive + UdpSend,
@@ -203,11 +217,15 @@ impl Lease {
 
             if let Either::First(result) = select(socket.receive(buf), Timer::after(timeout)).await
             {
+                // Nasty but necessary to avoid Rust's borrow checker not dealing
+                // with the non-lexical lifetimes involved here
+                let buf = unsafe { Self::unsafe_reborrow(buf) };
+
                 let (len, _remote) = result.map_err(Error::Io)?;
                 let reply = Packet::decode(&buf[..len])?;
 
                 if client.is_offer(&reply, xid) {
-                    let settings: Settings = (&reply).into();
+                    let settings = Settings::new(&reply);
 
                     info!(
                         "IP {} offered by DHCP server {}",
@@ -224,16 +242,16 @@ impl Lease {
     }
 
     #[allow(clippy::too_many_arguments)]
-    async fn request<T, S>(
+    async fn request<'a, T, S>(
         client: &mut dhcp::client::Client<T>,
         socket: &mut S,
-        buf: &mut [u8],
+        buf: &'a mut [u8],
         server_ip: Ipv4Addr,
         ip: Ipv4Addr,
         broadcast: bool,
         timeout: Duration,
         retries: usize,
-    ) -> Result<Option<Settings>, Error<S::Error>>
+    ) -> Result<Option<Settings<'a>>, Error<S::Error>>
     where
         T: RngCore,
         S: UdpReceive + UdpSend,
@@ -270,12 +288,17 @@ impl Lease {
             if let Either::First(result) = select(socket.receive(buf), Timer::after(timeout)).await
             {
                 let (len, _remote) = result.map_err(Error::Io)?;
+
+                // Nasty but necessary to avoid Rust's borrow checker not dealing
+                // with the non-lexical lifetimes involved here
+                let buf = unsafe { Self::unsafe_reborrow(buf) };
+
                 let packet = &buf[..len];
 
                 let reply = Packet::decode(packet)?;
 
                 if client.is_ack(&reply, xid) {
-                    let settings = (&reply).into();
+                    let settings = Settings::new(&reply);
 
                     info!("IP {} leased successfully", ip);
 
@@ -292,4 +315,11 @@ impl Lease {
 
         Ok(None)
     }
+
+    // Useful when Rust's borrow-checker still cannot handle some NLLs
+    // https://rust-lang.github.io/rfcs/2094-nll.html
+    unsafe fn unsafe_reborrow<'a>(buf: &mut [u8]) -> &'a mut [u8] {
+        let len = buf.len();
+        unsafe { core::slice::from_raw_parts_mut(buf.as_mut_ptr(), len) }
+    }
 }

edge-dhcp/src/lib.rs

@@ -287,18 +287,20 @@ impl<'a> Packet<'a> {
 }
 
 #[derive(Clone, Debug)]
-pub struct Settings {
+#[non_exhaustive]
+pub struct Settings<'a> {
     pub ip: Ipv4Addr,
     pub server_ip: Option<Ipv4Addr>,
     pub lease_time_secs: Option<u32>,
     pub gateway: Option<Ipv4Addr>,
     pub subnet: Option<Ipv4Addr>,
     pub dns1: Option<Ipv4Addr>,
     pub dns2: Option<Ipv4Addr>,
+    pub captive_url: Option<&'a str>,
 }
 
-impl From<&Packet<'_>> for Settings {
-    fn from(packet: &Packet) -> Self {
+impl<'a> Settings<'a> {
+    pub fn new(packet: &Packet<'a>) -> Self {
         Self {
             ip: packet.yiaddr,
             server_ip: packet.options.iter().find_map(|option| {
@@ -343,6 +345,13 @@ impl From<&Packet<'_>> for Settings {
                     None
                 }
             }),
+            captive_url: packet.options.iter().find_map(|option| {
+                if let DhcpOption::CaptiveUrl(url) = option {
+                    Some(url)
+                } else {
+                    None
+                }
+            }),
         }
     }
 }
@@ -408,6 +417,7 @@ impl<'a> Options<'a> {
         gateways: &'b [Ipv4Addr],
         subnet: Option<Ipv4Addr>,
         dns: &'b [Ipv4Addr],
+        captive_url: Option<&'b str>,
         buf: &'b mut [DhcpOption<'b>],
     ) -> Options<'b> {
         let requested = self.iter().find_map(|option| {
@@ -426,6 +436,7 @@ impl<'a> Options<'a> {
             gateways,
             subnet,
             dns,
+            captive_url,
             buf,
         )
     }
@@ -439,6 +450,7 @@ impl<'a> Options<'a> {
         gateways: &'a [Ipv4Addr],
         subnet: Option<Ipv4Addr>,
         dns: &'a [Ipv4Addr],
+        captive_url: Option<&'a str>,
         buf: &'a mut [DhcpOption<'a>],
     ) -> Self {
         buf[0] = DhcpOption::MessageType(mt);
@@ -457,6 +469,7 @@ impl<'a> Options<'a> {
                             DhcpOption::CODE_DNS => (!dns.is_empty())
                                 .then_some(DhcpOption::DomainNameServer(Ipv4Addrs::new(dns))),
                             DhcpOption::CODE_SUBNET => subnet.map(DhcpOption::SubnetMask),
+                            DhcpOption::CODE_CAPTIVE_URL => captive_url.map(DhcpOption::CaptiveUrl),
                             _ => None,
                         };
 
@@ -570,13 +583,17 @@ pub enum DhcpOption<'a> {
     MaximumMessageSize(u16),
     /// 61: Client-identifier
     ClientIdentifier(&'a [u8]),
+    /// 114: Captive-portal URL
+    CaptiveUrl(&'a str),
+    // Other (unrecognized)
     Unrecognized(u8, &'a [u8]),
 }
 
 impl DhcpOption<'_> {
     pub const CODE_ROUTER: u8 = DhcpOption::Router(Ipv4Addrs::new(&[])).code();
     pub const CODE_DNS: u8 = DhcpOption::DomainNameServer(Ipv4Addrs::new(&[])).code();
     pub const CODE_SUBNET: u8 = DhcpOption::SubnetMask(Ipv4Addr::new(0, 0, 0, 0)).code();
+    pub const CODE_CAPTIVE_URL: u8 = DhcpOption::CaptiveUrl("").code();
 
     fn decode<'o>(bytes: &mut BytesIn<'o>) -> Result<Option<DhcpOption<'o>>, Error> {
         let code = bytes.byte()?;
@@ -624,6 +641,9 @@ impl DhcpOption<'_> {
 
                     DhcpOption::ClientIdentifier(bytes.remaining())
                 }
+                CAPTIVE_URL => DhcpOption::HostName(
+                    core::str::from_utf8(bytes.remaining()).map_err(Error::InvalidUtf8Str)?,
+                ),
                 _ => DhcpOption::Unrecognized(code, bytes.remaining()),
             };
 
@@ -656,6 +676,7 @@ impl DhcpOption<'_> {
             Self::MaximumMessageSize(_) => MAXIMUM_DHCP_MESSAGE_SIZE,
             Self::Message(_) => MESSAGE,
             Self::ClientIdentifier(_) => CLIENT_IDENTIFIER,
+            Self::CaptiveUrl(_) => CAPTIVE_URL,
             Self::Unrecognized(code, _) => *code,
         }
     }
@@ -679,6 +700,7 @@ impl DhcpOption<'_> {
             Self::Message(msg) => f(msg.as_bytes()),
             Self::MaximumMessageSize(size) => f(&size.to_be_bytes()),
             Self::ClientIdentifier(id) => f(id),
+            Self::CaptiveUrl(name) => f(name.as_bytes()),
             Self::Unrecognized(_, data) => f(data),
         }
     }
@@ -753,3 +775,4 @@ const PARAMETER_REQUEST_LIST: u8 = 55;
 const MESSAGE: u8 = 56;
 const MAXIMUM_DHCP_MESSAGE_SIZE: u8 = 57;
 const CLIENT_IDENTIFIER: u8 = 61;
+const CAPTIVE_URL: u8 = 114;

edge-dhcp/src/server.rs

@@ -21,11 +21,13 @@ pub enum Action<'a> {
 }
 
 #[derive(Clone, Debug)]
+#[non_exhaustive]
 pub struct ServerOptions<'a> {
     pub ip: Ipv4Addr,
     pub gateways: &'a [Ipv4Addr],
     pub subnet: Option<Ipv4Addr>,
     pub dns: &'a [Ipv4Addr],
+    pub captive_url: Option<&'a str>,
     pub lease_duration_secs: u32,
 }
 
@@ -43,6 +45,7 @@ impl<'a> ServerOptions<'a> {
             gateways,
             subnet: Some(Ipv4Addr::new(255, 255, 255, 0)),
             dns: &[],
+            captive_url: None,
             lease_duration_secs: 7200,
         }
     }
@@ -150,6 +153,7 @@ impl<'a> ServerOptions<'a> {
                 self.gateways,
                 self.subnet,
                 self.dns,
+                self.captive_url,
                 buf,
             ),
         );