[pve-devel] [PATCH proxmox v4 2/2] network-types: add hostname type

[Stefan Hanreich]

Add a type for representing Linux hostnames. It enforces the same
constraints as the installer enforces [1], which are in turn taken
from the requirements Debian has for hostnames.

[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 v3 (thanks @Wolfgang):
    * improved validation logic
    * moved hostname to a specific debian module
    * added additional TryFrom implementations
    * added a unit test with a non-ASCII alphanumeric character
    
    Changes from v2:
    * improved hostname validation (thanks @Maximiliano @Christoph)
    * added additional unit tests
    
    Changes from v1:
    * added unit tests

 proxmox-network-types/src/debian.rs | 113 ++++++++++++++++++++++++++++
 proxmox-network-types/src/lib.rs    |   1 +
 2 files changed, 114 insertions(+)
 create mode 100644 proxmox-network-types/src/debian.rs

diff --git a/proxmox-network-types/src/debian.rs b/proxmox-network-types/src/debian.rs
new file mode 100644
index 00000000..7acd55ca
--- /dev/null
+++ b/proxmox-network-types/src/debian.rs
@@ -0,0 +1,113 @@
+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 has an invalid format")]
+    InvalidFormat,
+}
+
+/// Hostname of a Debian system
+///
+/// It checks for the following conditions:
+/// * At most 63 characters long.
+/// * It must not start or end with a hyphen.
+/// * Must only contain ASCII alphanumeric characters as well as hyphens.
+/// * It must not be purely numerical.
+#[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.to_string())
+    }
+}
+
+impl AsRef<str> for Hostname {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
+
+impl TryFrom<&str> for Hostname {
+    type Error = HostnameError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        value.parse()
+    }
+
+}
+
+impl TryFrom<String> for Hostname {
+    type Error = HostnameError;
+
+    fn try_from(value: String) -> Result<Self, Self::Error> {
+        Hostname::new(value)
+    }
+
+}
+
+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
+    pub fn new(name: String) -> Result<Self, HostnameError> {
+        if name.is_empty() || name.len() > 63 {
+            return Err(HostnameError::InvalidLength);
+        }
+
+        if !name.chars().all(|c| c.is_ascii_alphanumeric() || c == '-') {
+            return Err(HostnameError::InvalidFormat);
+        }
+
+        if name.starts_with('-') || name.ends_with('-') {
+            return Err(HostnameError::InvalidFormat);
+        }
+
+        if name.chars().all(|c| c.is_ascii_digit()) {
+            return Err(HostnameError::InvalidFormat);
+        }
+
+        Ok(Self(name))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_hostname() {
+        for valid_hostname in [
+            "debian",
+            "0host",
+            "some-host-123",
+            "63characterlonghostnamexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+        ] {
+            Hostname::new(valid_hostname.to_string()).expect("valid hostname");
+        }
+
+        for invalid_hostname in [
+            "-debian",
+            "0host-",
+            "some/host",
+            "",
+            "123",
+            "64characterlonghostnamexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
+            "🆒",
+            "Ɖ",
+        ] {
+            Hostname::new(invalid_hostname.to_string()).expect_err("invalid hostname");
+        }
+    }
+}
diff --git a/proxmox-network-types/src/lib.rs b/proxmox-network-types/src/lib.rs
index b952d71c..9151348a 100644
--- a/proxmox-network-types/src/lib.rs
+++ b/proxmox-network-types/src/lib.rs
@@ -1,2 +1,3 @@
+pub mod debian;
 pub mod ip_address;
 pub mod mac_address;
-- 
2.39.5