Use at-commands crate and support DNS

* Use at-commands for building and parsing AT commands which has better
  error handling.
* Retrieve DNS servers
* Retrieve gateway
* Update example to configure embassy-net with retrieved parameters.

4 files changed, 129 insertions, 159 deletions

diff --git a/embassy-net-nrf91/Cargo.toml b/embassy-net-nrf91/Cargo.toml
index e2d596d59..07a0c8886 100644
--- a/embassy-net-nrf91/Cargo.toml
+++ b/embassy-net-nrf91/Cargo.toml
@@ -26,6 +26,7 @@ embassy-net-driver-channel = { version = "0.3.0", path = "../embassy-net-driver-
 
 heapless = "0.8"
 embedded-io = "0.6.1"
+at-commands = "0.5.4"
 
 [package.metadata.embassy_docs]
 src_base = "https://github.com/embassy-rs/embassy/blob/embassy-net-nrf91-v$VERSION/embassy-net-nrf91/src/"
diff --git a/embassy-net-nrf91/src/context.rs b/embassy-net-nrf91/src/context.rs
index c47b1ade6..b532dca14 100644
--- a/embassy-net-nrf91/src/context.rs
+++ b/embassy-net-nrf91/src/context.rs
@@ -2,6 +2,8 @@ use core::net::IpAddr;
 use heapless::String;
 use core::str::FromStr;
 use core::fmt::Write;
+use heapless::Vec;
+use at_commands::{builder::CommandBuilder, parser::CommandParser};
 
 /// Provides a higher level API for configuring and reading information for a given
 /// context id.
@@ -28,10 +30,17 @@ pub enum AuthProt {
 pub enum Error {
     BufferTooSmall,
     AtCommand,
+    AtParseError,
     AddrParseError,
     Format,
 }
 
+impl From<at_commands::parser::ParseError> for Error {
+    fn from(_: at_commands::parser::ParseError) -> Self {
+        Self::AtParseError
+    }
+}
+
 impl From<core::fmt::Error> for Error {
     fn from(_: core::fmt::Error) -> Self {
         Self::Format
@@ -42,6 +51,8 @@ impl From<core::fmt::Error> for Error {
 pub struct Status {
     pub attached: bool,
     pub ip: Option<IpAddr>,
+    pub gateway: Option<IpAddr>,
+    pub dns: Vec<IpAddr, 2>,
 }
 
 #[cfg(feature = "defmt")]
@@ -67,129 +78,122 @@ impl<'a> Control<'a> {
 
     /// Configures the modem with the provided config.
     pub async fn configure(&self, config: Config<'_>) -> Result<(), Error> {
-        let mut cmd: String<128> = String::new();
+        let mut cmd: [u8; 256] = [0; 256];
         let mut buf: [u8; 256] = [0; 256];
 
-        write!(cmd, "AT+CGDCONT={},\"IP\",\"{}\"", self.cid, config.gateway).map_err(|_| Error::BufferTooSmall)?;
-        let n = self.control.at_command(cmd.as_bytes(), &mut buf).await;
-        let mut res = &buf[..n];
-        let res = split_field(&mut res);
-        if res != b"OK" {
-            return Err(Error::AtCommand)
-        }
-        cmd.clear();
-
-        write!(cmd, "AT+CGAUTH={},{}", self.cid, config.auth_prot as u8)?;
+        let op = CommandBuilder::create_set(&mut cmd, true)
+            .named("+CGDCONT")
+            .with_int_parameter(self.cid)
+            .with_string_parameter("IP")
+            .with_string_parameter(config.gateway)
+            .finish().map_err(|_| Error::BufferTooSmall)?;
+        let n = self.control.at_command(op, &mut buf).await;
+        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;
+
+        let mut op = CommandBuilder::create_set(&mut cmd, true)
+            .named("+CGAUTH")
+            .with_int_parameter(self.cid)
+            .with_int_parameter(config.auth_prot as u8);
         if let Some((username, password)) = config.auth {
-            write!(cmd, ",\"{}\",\"{}\"", username, password).map_err(|_| Error::BufferTooSmall)?;
-        }
-        let n = self.control.at_command(cmd.as_bytes(), &mut buf).await;
-        let mut res = &buf[..n];
-        let res = split_field(&mut res);
-        if res != b"OK" {
-            return Err(Error::AtCommand)
+            op = op.with_string_parameter(username).with_string_parameter(password);
         }
-        cmd.clear();
+        let op = op.finish().map_err(|_| Error::BufferTooSmall)?;
 
-        let n = self.control.at_command(b"AT+CFUN=1", &mut buf).await;
-        let mut res = &buf[..n];
-        let res = split_field(&mut res);
-        if res != b"OK" {
-            return Err(Error::AtCommand);
-        }
+        let n = self.control.at_command(op, &mut buf).await;
+        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;
+
+        let op = CommandBuilder::create_set(&mut cmd, true)
+            .named("+CFUN")
+            .with_int_parameter(1)
+            .finish().map_err(|_| Error::BufferTooSmall)?;
+        let n = self.control.at_command(op, &mut buf).await;
+        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;
 
         Ok(())
     }
 
     pub async fn status(&self) -> Result<Status, Error> {
+        let mut cmd: [u8; 256] = [0; 256];
         let mut buf: [u8; 256] = [0; 256];
-        let n = self.control.at_command(b"AT+CGATT?", &mut buf).await;
-        let mut res = &buf[..n];
-        pop_prefix(&mut res, b"+CGATT: ");
-        let res = split_field(&mut res);
-        let attached = res == b"1";
 
+        let op = CommandBuilder::create_query(&mut cmd, true)
+            .named("+CGATT")
+            .finish().map_err(|_| Error::BufferTooSmall)?;
+        let n = self.control.at_command(op, &mut buf).await;
+        let (res, ) = CommandParser::parse(&buf[..n])
+            .expect_identifier(b"+CGATT: ")
+            .expect_int_parameter()
+            .expect_identifier(b"\r\nOK").finish()?;
+        let attached = res == 1;
         if !attached {
-            return Ok(Status { attached, ip: None })
+            return Ok(Status { attached, ip: None, gateway: None, dns: Vec::new() })
         }
 
-        let mut s: String<128> = String::new();
-        write!(s, "AT+CGPADDR={}", self.cid)?;
-        let n = self.control.at_command(s.as_bytes(), &mut buf).await;
-        let mut res = &buf[..n];
-        s.clear();
-
-        write!(s, "+CGPADDR: {},", self.cid)?;
-
-        if s.len() > res.len() {
-            let res = split_field(&mut res);
-            if res == b"OK" {
-                Ok(Status { attached, ip: None })
+        let op = CommandBuilder::create_set(&mut cmd, true)
+            .named("+CGPADDR")
+            .with_int_parameter(self.cid)
+            .finish().map_err(|_| Error::BufferTooSmall)?;
+        let n = self.control.at_command(op, &mut buf).await;
+        let (_, ip1, ip2, ) = CommandParser::parse(&buf[..n])
+            .expect_identifier(b"+CGPADDR: ")
+            .expect_int_parameter()
+            .expect_optional_string_parameter()
+            .expect_optional_string_parameter()
+            .expect_identifier(b"\r\nOK").finish()?;
+
+        let ip = if let Some(ip) = ip1 {
+            let ip = IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?;
+            self.control.open_raw_socket().await;
+            Some(ip)
+        } else {
+            None
+        };
+
+        let op = CommandBuilder::create_set(&mut cmd, true)
+            .named("+CGCONTRDP")
+            .with_int_parameter(self.cid)
+            .finish().map_err(|_| Error::BufferTooSmall)?;
+        let n = self.control.at_command(op, &mut buf).await;
+        let (_cid, _bid, _apn, _mask, gateway, dns1, dns2, _, _, _, _, mtu) = CommandParser::parse(&buf[..n])
+            .expect_identifier(b"+CGCONTRDP: ")
+            .expect_int_parameter()
+            .expect_optional_int_parameter()
+            .expect_optional_string_parameter()
+            .expect_optional_string_parameter()
+            .expect_optional_string_parameter()
+            .expect_optional_string_parameter()
+            .expect_optional_string_parameter()
+            .expect_optional_int_parameter()
+            .expect_optional_int_parameter()
+            .expect_optional_int_parameter()
+            .expect_optional_int_parameter()
+            .expect_optional_int_parameter()
+            .expect_identifier(b"\r\nOK").finish()?;
+
+        let gateway = if let Some(ip) = gateway {
+            if ip.is_empty() {
+                None
             } else {
-                Err(Error::AtCommand)
+                Some(IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?)
             }
         } else {
-            pop_prefix(&mut res, s.as_bytes());
+            None
+        };
 
-            let ip = split_field(&mut res);
-            if !ip.is_empty() {
-                let ip = IpAddr::from_str(unsafe { core::str::from_utf8_unchecked(ip) }).map_err(|_| Error::AddrParseError)?;
-                self.control.open_raw_socket().await;
-                Ok(Status { attached, ip: Some(ip) })
-            } else {
-                Ok(Status { attached, ip: None })
-            }
+        let mut dns = Vec::new();
+        if let Some(ip) = dns1 {
+            dns.push(IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?).unwrap();
         }
-    }
-}
 
-pub(crate) fn is_whitespace(char: u8) -> bool {
-    match char {
-        b'\r' | b'\n' | b' ' => true,
-        _ => false,
-    }
-}
-
-pub(crate) fn is_separator(char: u8) -> bool {
-    match char {
-        b',' | b'\r' | b'\n' | b' ' => true,
-        _ => false,
-    }
-}
-
-pub(crate) fn split_field<'a>(data: &mut &'a [u8]) -> &'a [u8] {
-    while !data.is_empty() && is_whitespace(data[0]) {
-        *data = &data[1..];
-    }
-
-    if data.is_empty() {
-        return &[];
-    }
-
-    if data[0] == b'"' {
-        let data2 = &data[1..];
-        let end = data2.iter().position(|&x| x == b'"').unwrap_or(data2.len());
-        let field = &data2[..end];
-        let mut rest = &data2[data2.len().min(end + 1)..];
-        if rest.first() == Some(&b'\"') {
-            rest = &rest[1..];
-        }
-        while !rest.is_empty() && is_separator(rest[0]) {
-            rest = &rest[1..];
+        if let Some(ip) = dns2 {
+            dns.push(IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?).unwrap();
         }
-        *data = rest;
-        field
-    } else {
-        let end = data.iter().position(|&x| is_separator(x)).unwrap_or(data.len());
-        let field = &data[0..end];
-        let rest = &data[data.len().min(end + 1)..];
-        *data = rest;
-        field
-    }
-}
 
-pub(crate) fn pop_prefix(data: &mut &[u8], prefix: &[u8]) {
-    assert!(data.len() >= prefix.len());
-    assert!(&data[..prefix.len()] == prefix);
-    *data = &data[prefix.len()..];
+        Ok(Status {
+            attached,
+            ip,
+            gateway,
+            dns,
+        })
+    }
 }
diff --git a/examples/nrf9160/Cargo.toml b/examples/nrf9160/Cargo.toml
index fc24e99d2..9aeb99317 100644
--- a/examples/nrf9160/Cargo.toml
+++ b/examples/nrf9160/Cargo.toml
@@ -14,6 +14,7 @@ embassy-net = { version = "0.4.0", path = "../../embassy-net", features = ["defm
 defmt = "0.3"
 defmt-rtt = "0.4"
 
+heapless = "0.8"
 cortex-m = { version = "0.7.6", features = ["inline-asm", "critical-section-single-core"] }
 cortex-m-rt = "0.7.0"
 panic-probe = { version = "0.3", features = ["print-defmt"] }
diff --git a/examples/nrf9160/src/bin/modem_tcp_client.rs b/examples/nrf9160/src/bin/modem_tcp_client.rs
index 817ad17c7..f80861693 100644
--- a/examples/nrf9160/src/bin/modem_tcp_client.rs
+++ b/examples/nrf9160/src/bin/modem_tcp_client.rs
@@ -5,9 +5,10 @@ use core::mem::MaybeUninit;
 use core::net::IpAddr;
 use core::ptr::addr_of_mut;
 use core::str::FromStr;
-use core::{slice, str};
+use core::slice;
 
 use defmt::{assert, info, warn, unwrap};
+use heapless::Vec;
 use embassy_executor::Spawner;
 use embassy_net::{Ipv4Address, Ipv4Cidr, Stack, StackResources};
 use embassy_net_nrf91::{Runner, State, context};
@@ -146,10 +147,23 @@ async fn main(spawner: Spawner) {
     };
     let addr = Ipv4Address(addr.octets());
 
+    let gateway = if let Some(IpAddr::V4(addr)) = status.gateway {
+        Some(Ipv4Address(addr.octets()))
+    } else {
+        None
+    };
+
+    let mut dns_servers = Vec::new();
+    for dns in status.dns {
+        if let IpAddr::V4(ip) = dns {
+            unwrap!(dns_servers.push(Ipv4Address(ip.octets())));
+        }
+    }
+
     stack.set_config_v4(embassy_net::ConfigV4::Static(embassy_net::StaticConfigV4 {
         address: Ipv4Cidr::new(addr, 32),
-        gateway: None,
-        dns_servers: Default::default(),
+        gateway,
+        dns_servers,
     }));
 
     let mut rx_buffer = [0; 4096];
@@ -159,15 +173,16 @@ async fn main(spawner: Spawner) {
         socket.set_timeout(Some(Duration::from_secs(10)));
 
         info!("Connecting...");
-        let host_addr = embassy_net::Ipv4Address::from_str("83.51.182.206").unwrap();
-        if let Err(e) = socket.connect((host_addr, 8000)).await {
+        let host_addr = embassy_net::Ipv4Address::from_str("45.79.112.203").unwrap();
+        if let Err(e) = socket.connect((host_addr, 4242)).await {
             warn!("connect error: {:?}", e);
+            Timer::after_secs(1).await;
             continue;
         }
         info!("Connected to {:?}", socket.remote_endpoint());
 
         let msg = b"Hello world!\n";
-        loop {
+        for _ in 0..10 {
             if let Err(e) = socket.write_all(msg).await {
                 warn!("write error: {:?}", e);
                 break;
@@ -177,54 +192,3 @@ async fn main(spawner: Spawner) {
         }
     }
 }
-
-fn is_whitespace(char: u8) -> bool {
-    match char {
-        b'\r' | b'\n' | b' ' => true,
-        _ => false,
-    }
-}
-
-fn is_separator(char: u8) -> bool {
-    match char {
-        b',' | b'\r' | b'\n' | b' ' => true,
-        _ => false,
-    }
-}
-
-fn split_field<'a>(data: &mut &'a [u8]) -> &'a [u8] {
-    while !data.is_empty() && is_whitespace(data[0]) {
-        *data = &data[1..];
-    }
-
-    if data.is_empty() {
-        return &[];
-    }
-
-    if data[0] == b'"' {
-        let data2 = &data[1..];
-        let end = data2.iter().position(|&x| x == b'"').unwrap_or(data2.len());
-        let field = &data2[..end];
-        let mut rest = &data2[data2.len().min(end + 1)..];
-        if rest.first() == Some(&b'\"') {
-            rest = &rest[1..];
-        }
-        while !rest.is_empty() && is_separator(rest[0]) {
-            rest = &rest[1..];
-        }
-        *data = rest;
-        field
-    } else {
-        let end = data.iter().position(|&x| is_separator(x)).unwrap_or(data.len());
-        let field = &data[0..end];
-        let rest = &data[data.len().min(end + 1)..];
-        *data = rest;
-        field
-    }
-}
-
-fn pop_prefix(data: &mut &[u8], prefix: &[u8]) {
-    assert!(data.len() >= prefix.len());
-    assert!(&data[..prefix.len()] == prefix);
-    *data = &data[prefix.len()..];
-}