DHCP support for core device firmware

DHCP is enabled by setting the `ip` config entry to "use_dhcp". Reusing this
config field rather than creating a new one means that there is no ambiguity
over which config field takes precedence.

Adds a thread to configure the interface based on DHCP events
Adds a `Dhcpv4Socket` as a wrapper around smoltcp's version
Formalises the storage of the IP addresses so that we can update one in
another module.

There's also a workaround for the first DHCP discover packet frequently
going missing.

Signed-off-by: Michael Birtwell <michael.birtwell@oxionics.com>

RELEASE_NOTES.rst

@@ -42,6 +42,7 @@ Highlights:
 * ``PCA9548`` I2C switch class renamed to ``I2CSwitch``, to accomodate support for PCA9547, and
   possibly other switches in future. Readback has been removed, and now only one channel per 
   switch is supported.
+* The "ip" config option can now be set to "use_dhcp" to use DHCP to obtain an IP address.
 
 Breaking changes:
 

artiq/firmware/libboard_misoc/net_settings.rs

@@ -1,12 +1,15 @@
 use core::fmt;
 
-use smoltcp::wire::{EthernetAddress, IpAddress};
+use smoltcp::wire::{EthernetAddress, IpAddress, Ipv4Address};
 
 use config;
 #[cfg(soc_platform = "kasli")]
 use i2c_eeprom;
 
 
+pub const USE_DHCP: IpAddress = IpAddress::Ipv4(Ipv4Address::UNSPECIFIED);
+
+
 pub struct NetAddresses {
     pub hardware_addr: EthernetAddress,
     pub ipv4_addr: IpAddress,
@@ -49,7 +52,13 @@ pub fn get_adresses() -> NetAddresses {
     }
 
     let ipv4_addr;
-    match config::read_str("ip", |r| r.map(|s| s.parse())) {
+    match config::read_str("ip", |r| r.map(|s| {
+        if s == "use_dhcp" {
+            Ok(USE_DHCP)
+        } else {
+            s.parse()
+        }
+    })) {
         Ok(Ok(addr)) => ipv4_addr = addr,
         _ => {
             #[cfg(soc_platform = "kasli")]

artiq/firmware/runtime/Cargo.toml

@@ -27,9 +27,13 @@ board_misoc = { path = "../libboard_misoc", features = ["uart_console", "smoltcp
 logger_artiq = { path = "../liblogger_artiq" }
 board_artiq = { path = "../libboard_artiq" }
 proto_artiq = { path = "../libproto_artiq", features = ["log", "alloc"] }
-smoltcp = { version = "0.8.0", default-features = false, features = ["alloc", "medium-ethernet", "proto-ipv4", "proto-ipv6", "socket-tcp"] }
 riscv = { version = "0.6.0", features = ["inline-asm"] }
 
+[dependencies.smoltcp]
+version = "0.8.0"
+default-features = false
+features = ["alloc", "medium-ethernet", "proto-ipv4", "proto-ipv6", "socket-tcp", "socket-dhcpv4"]
+
 [dependencies.fringe]
 git = "https://git.m-labs.hk/M-Labs/libfringe.git"
 rev = "3ecbe5"

artiq/firmware/runtime/dhcp.rs

@@ -0,0 +1,59 @@
+use board_misoc::clock;
+use sched;
+use sched::Dhcpv4Socket;
+use smoltcp::socket::Dhcpv4Event;
+use smoltcp::wire::{Ipv4Address, Ipv4Cidr};
+
+pub fn dhcp_thread(io: sched::Io) {
+    let mut socket = Dhcpv4Socket::new(&io);
+    let mut last_ip: Option<Ipv4Cidr> = None;
+    let mut done_reset = false;
+    let start_time = clock::get_ms();
+
+    loop {
+        // A significant amount of the time our first discover isn't received
+        // by the server. This is likely to be because the ethernet device isn't quite
+        // ready at the point that it is sent. The following makes recovery from
+        // that faster.
+        if !done_reset && last_ip.is_none() && start_time + 1000 < clock::get_ms() {
+            info!("Didn't get initial IP in first second. Assuming packet loss, trying a reset.");
+            socket.reset();
+            done_reset = true;
+        }
+        if let Some(event) = socket.poll() {
+            match event {
+                Dhcpv4Event::Configured(config) => {
+                    // Only compare the ip address in the config with previous config because we
+                    // ignore the rest of the config i.e. we don't do any DNS or require a default
+                    // gateway.
+                    let changed = if let Some(last_ip) = last_ip {
+                        if config.address != last_ip {
+                            info!("IP address changed {} -> {}", last_ip, config.address);
+                            true
+                        } else {
+                            false
+                        }
+                    } else {
+                        info!("Acquired IP address: None -> {}", config.address);
+                        true
+                    };
+                    if changed {
+                        last_ip = Some(config.address);
+                        io.set_ipv4_address(&config.address);
+                    }
+                }
+                Dhcpv4Event::Deconfigured => {
+                    if let Some(ip) = last_ip {
+                        info!("Lost IP address {} -> None", ip);
+                        io.set_ipv4_address(&Ipv4Cidr::new(Ipv4Address::UNSPECIFIED, 0));
+                        last_ip = None;
+                    }
+                    // We always get one of these events at the start, ignore that one
+                }
+            }
+        }
+        // We want to poll after every poll of the interface. So we need to
+        // do a minimal yield here.
+        io.relinquish().unwrap();
+    }
+}

artiq/firmware/runtime/main.rs

@@ -27,11 +27,12 @@ extern crate riscv;
 
 use core::cell::RefCell;
 use core::convert::TryFrom;
-use smoltcp::wire::{IpCidr, HardwareAddress};
+use smoltcp::wire::{HardwareAddress, IpAddress, IpCidr, Ipv4Address};
 
 use board_misoc::{csr, ident, clock, spiflash, config, net_settings, pmp, boot};
 #[cfg(has_ethmac)]
 use board_misoc::ethmac;
+use board_misoc::net_settings::{NetAddresses, USE_DHCP};
 #[cfg(has_drtio)]
 use board_artiq::drtioaux;
 use board_artiq::drtio_routing;
@@ -58,6 +59,14 @@ mod session;
 mod moninj;
 #[cfg(has_rtio_analyzer)]
 mod analyzer;
+mod dhcp;
+
+// Fixed indexes for the IP addresses so that they can be modified with some
+// semblance of confidence
+pub const IPV4_INDEX: usize = 0;
+pub const IPV6_LL_INDEX: usize = 1;
+pub const IPV6_INDEX: usize = 2;
+const IP_ADDRESS_STORAGE_SIZE: usize = 3;
 
 #[cfg(has_grabber)]
 fn grabber_thread(io: sched::Io) {
@@ -87,6 +96,18 @@ fn setup_log_levels() {
     }
 }
 
+pub fn get_ip_addrs(net_addresses: &NetAddresses) -> [IpCidr; IP_ADDRESS_STORAGE_SIZE] {
+    let mut storage = [
+        IpCidr::new(IpAddress::Ipv4(Ipv4Address::UNSPECIFIED), 0);  IP_ADDRESS_STORAGE_SIZE
+    ];
+    storage[IPV4_INDEX] = IpCidr::new(net_addresses.ipv4_addr, 0);
+    storage[IPV6_LL_INDEX] = IpCidr::new(net_addresses.ipv6_ll_addr, 0);
+    if let Some(ipv6) = net_addresses.ipv6_addr {
+        storage[IPV6_INDEX] = IpCidr::new(ipv6, 0);
+    }
+    storage
+}
+
 fn startup() {
     clock::init();
     info!("ARTIQ runtime starting...");
@@ -141,31 +162,17 @@ fn startup() {
         smoltcp::iface::NeighborCache::new(alloc::collections::btree_map::BTreeMap::new());
     let net_addresses = net_settings::get_adresses();
     info!("network addresses: {}", net_addresses);
-    let interface = match net_addresses.ipv6_addr {
-        Some(addr) => {
-            let ip_addrs = [
-                IpCidr::new(net_addresses.ipv4_addr, 0),
-                IpCidr::new(net_addresses.ipv6_ll_addr, 0),
-                IpCidr::new(addr, 0)
-            ];
-            smoltcp::iface::InterfaceBuilder::new(net_device, vec![])
-                       .hardware_addr(HardwareAddress::Ethernet(net_addresses.hardware_addr))
-                       .ip_addrs(ip_addrs)
-                       .neighbor_cache(neighbor_cache)
-                       .finalize()
-        }
-        None => {
-            let ip_addrs = [
-                IpCidr::new(net_addresses.ipv4_addr, 0),
-                IpCidr::new(net_addresses.ipv6_ll_addr, 0)
-            ];
-            smoltcp::iface::InterfaceBuilder::new(net_device, vec![])
-                       .hardware_addr(HardwareAddress::Ethernet(net_addresses.hardware_addr))
-                       .ip_addrs(ip_addrs)
-                       .neighbor_cache(neighbor_cache)
-                       .finalize()
-        }
+    let use_dhcp = if net_addresses.ipv4_addr == USE_DHCP {
+        info!("Will try to acquire an IPv4 address with DHCP");
+        true
+    } else {
+        false
     };
+    let interface = smoltcp::iface::InterfaceBuilder::new(net_device, vec![])
+        .hardware_addr(HardwareAddress::Ethernet(net_addresses.hardware_addr))
+        .ip_addrs(get_ip_addrs(&net_addresses))
+        .neighbor_cache(neighbor_cache)
+        .finalize();
 
     #[cfg(has_drtio)]
     let drtio_routing_table = urc::Urc::new(RefCell::new(
@@ -182,6 +189,10 @@ fn startup() {
     let mut scheduler = sched::Scheduler::new(interface);
     let io = scheduler.io();
 
+    if use_dhcp {
+        io.spawn(4096, dhcp::dhcp_thread);
+    }
+
     rtio_mgt::startup(&io, &aux_mutex, &drtio_routing_table, &up_destinations);
 
     io.spawn(4096, mgmt::thread);

artiq/firmware/runtime/sched.rs

@@ -2,13 +2,13 @@
 
 use core::mem;
 use core::result;
-use core::cell::{Cell, RefCell};
+use core::cell::{Cell, RefCell, RefMut};
 use alloc::vec::Vec;
 use fringe::OwnedStack;
 use fringe::generator::{Generator, Yielder, State as GeneratorState};
 use smoltcp::time::Duration;
 use smoltcp::Error as NetworkError;
-use smoltcp::wire::IpEndpoint;
+use smoltcp::wire::{IpEndpoint, Ipv4Cidr, IpCidr};
 use smoltcp::iface::{Interface, SocketHandle};
 
 use io::{Read, Write};
@@ -16,6 +16,7 @@ use board_misoc::clock;
 use urc::Urc;
 use board_misoc::ethmac::EthernetDevice;
 use smoltcp::phy::Tracer;
+use IPV4_INDEX;
 
 #[derive(Fail, Debug)]
 pub enum Error {
@@ -273,6 +274,12 @@ impl<'a> Io<'a> {
     pub fn join(&self, handle: ThreadHandle) -> Result<(), Error> {
         self.until(move || handle.terminated())
     }
+
+    pub fn set_ipv4_address(&self, addr: &Ipv4Cidr) {
+        self.network.borrow_mut().update_ip_addrs(|addrs| {
+            addrs.as_mut()[IPV4_INDEX] = IpCidr::Ipv4(*addr);
+        })
+    }
 }
 
 #[derive(Clone)]
@@ -563,3 +570,45 @@ impl<'a> Drop for TcpStream<'a> {
         self.io.network.borrow_mut().remove_socket(self.handle);
     }
 }
+
+pub struct Dhcpv4Socket<'a> {
+    io: &'a Io<'a>,
+    handle: SocketHandle,
+}
+
+impl<'a> Dhcpv4Socket<'a> {
+
+    fn new_lower(io: &'a Io<'a>) -> SocketHandle {
+        let socket = smoltcp::socket::Dhcpv4Socket::new();
+        io.network.borrow_mut().add_socket(socket)
+    }
+
+    pub fn new(io: &'a Io<'a>) -> Self {
+        Self {
+            io,
+            handle: Self::new_lower(io)
+        }
+    }
+
+    fn lower(&mut self) -> RefMut<smoltcp::socket::Dhcpv4Socket> {
+        RefMut::map(
+            self.io.network.borrow_mut(),
+            |network| network.get_socket::<smoltcp::socket::Dhcpv4Socket>(self.handle),
+        )
+    }
+
+    pub fn poll(&mut self) -> Option<smoltcp::socket::Dhcpv4Event> {
+        self.lower().poll()
+    }
+
+    pub fn reset(&mut self) {
+        self.lower().reset()
+    }
+}
+
+impl<'a> Drop for Dhcpv4Socket<'a> {
+    fn drop(&mut self) {
+        let mut network = self.io.network.borrow_mut();
+        network.remove_socket(self.handle);
+    }
+}

doc/manual/installing.rst

@@ -268,6 +268,12 @@ In other cases, install OpenOCD as before, and flash the IP (and, if necessary,
 
 For Kasli devices, flashing a MAC address is not necessary as they can obtain it from their EEPROM.
 
+Alternatively you can set the "ip" config field to "use_dhcp" to have the device use DHCP to obtain an IP address on
+boot. e.g. ::
+
+  $ artiq_mkfs flash_storage.img -s ip use_dhcp
+  $ artiq_flash -t [board] -V [variant] -f flash_storage.img storage start
+
 Check that you can ping the device. If ping fails, check that the Ethernet link LED is ON - on Kasli, it is the LED next to the SFP0 connector. As a next step, look at the messages emitted on the UART during boot. Use a program such as flterm or PuTTY to connect to the device's serial port at 115200bps 8-N-1 and reboot the device. On Kasli, the serial port is on FTDI channel 2 with v1.1 hardware (with channel 0 being JTAG) and on FTDI channel 1 with v1.0 hardware.
 
 If you want to use IPv6, the device also has a link-local address that corresponds to its EUI-64, and an additional arbitrary IPv6 address can be defined by using the ``ip6`` configuration key. All IPv4 and IPv6 addresses can be used at the same time.