[pve-devel] [PATCH proxmox v2 2/2] network-types: add hostname type

[Stefan Hanreich]

Add a type for representing Linux hostnames. These are the same
constraints as the installer enforces [1]. Lowercasing is fine as
well, since practically everything treats hostnames case-insensitively
as RFC 952 stipulates:

> No distinction is made between upper and lower case.

[1] https://git.proxmox.com/?p=pve-installer.git;a=blob;f=Proxmox/Sys/Net.pm;h=81cb15f0042b195461324fffeca53d732133629e;hb=HEAD#l11
[2] https://www.rfc-editor.org/rfc/rfc952.txt

Signed-off-by: Stefan Hanreich <s.hanreich at proxmox.com>
---

Notes:
    sending this separately because this contains the new types, that
    haven't been a part of proxmox-ve-rs before.
    
    Changes from v1:
    * added unit tests

 proxmox-network-types/src/hostname.rs | 94 +++++++++++++++++++++++++++
 proxmox-network-types/src/lib.rs      |  1 +
 2 files changed, 95 insertions(+)
 create mode 100644 proxmox-network-types/src/hostname.rs

diff --git a/proxmox-network-types/src/hostname.rs b/proxmox-network-types/src/hostname.rs
new file mode 100644
index 00000000..ebe79986
--- /dev/null
+++ b/proxmox-network-types/src/hostname.rs
@@ -0,0 +1,94 @@
+use std::fmt::Display;
+
+use serde::{Deserialize, Serialize};
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum HostnameError {
+    #[error("the hostname must be from 1 to 63 characters long")]
+    InvalidLength,
+    #[error("the hostname contains invalid symbols")]
+    InvalidSymbols,
+}
+
+/// Hostname of a Linux machine
+///
+/// A hostname is at most 63 characters long and must only contain lowercase alphanumeric
+/// characters as well as hyphens. It must not start or end with a hyphen.
+#[derive(Debug, Deserialize, Serialize, Clone, Eq, Hash, PartialOrd, Ord, PartialEq)]
+pub struct Hostname(String);
+
+impl std::str::FromStr for Hostname {
+    type Err = HostnameError;
+
+    fn from_str(hostname: &str) -> Result<Self, Self::Err> {
+        Self::new(hostname)
+    }
+}
+
+impl AsRef<str> for Hostname {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
+
+impl Display for Hostname {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl Hostname {
+    /// Constructs a new hostname from a string
+    ///
+    /// This function accepts characters in any case, but the resulting hostname will be
+    /// lowercased.
+    pub fn new(name: impl AsRef<str>) -> Result<Self, HostnameError> {
+        let name_ref = name.as_ref();
+
+        if !(1..63).contains(&name_ref.len()) {
+            return Err(HostnameError::InvalidLength);
+        }
+
+        let host_name = name_ref.to_lowercase();
+
+        let mut characters = host_name.chars();
+
+        // first character must not be a hyphen
+        // SAFETY: ok because of length check
+        if !characters.next().unwrap().is_alphanumeric() {
+            return Err(HostnameError::InvalidSymbols);
+        }
+
+        if !characters.all(|c| c.is_alphanumeric() || c == '-') {
+            return Err(HostnameError::InvalidSymbols);
+        }
+
+        // last character must not be a hyphen
+        // SAFETY: ok because of length check
+        if !host_name.chars().next_back().unwrap().is_alphanumeric() {
+            return Err(HostnameError::InvalidSymbols);
+        }
+
+        Ok(Self(host_name))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_hostname() {
+        for valid_hostname in ["debian", "0host", "some-host-123", "123"] {
+            Hostname::new(valid_hostname).expect("valid hostname");
+        }
+
+        for invalid_hostname in ["-debian", "0host-", "some/host", "", "thisisawaywaywaytoolonghostnameheremustnotbemorethan63characters"] {
+            Hostname::new(invalid_hostname).expect_err("invalid hostname");
+        }
+
+        let uppercased_hostname = Hostname::new("UPPERCASE").expect("valid hostname");
+        assert_eq!(uppercased_hostname.as_ref(), "uppercase");
+    }
+}
diff --git a/proxmox-network-types/src/lib.rs b/proxmox-network-types/src/lib.rs
index b952d71c..f4812146 100644
--- a/proxmox-network-types/src/lib.rs
+++ b/proxmox-network-types/src/lib.rs
@@ -1,2 +1,3 @@
+pub mod hostname;
 pub mod ip_address;
 pub mod mac_address;
-- 
2.39.5