add login banner service

Modeled after the one from PVE, but using rust instead of perl for
resolving the nodename and writing to /etc/issue

Behavior differs a bit. We write all non-loopback addresses to this
file, as the gui accepts connections from them all, so limiting it to
the first one is not really sensible.
Further an error to resolve, or only getting loopback addresses won't
write out an empty /etc/issue file, but a note about the error at the
place where the address would be displayed.

Named it "pbsbanner", not "proxmox-backup-banner" as it's rather an
internal tool anyway and mirrors pvebanner, pmgbanner

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

Makefile

@@ -12,7 +12,8 @@ USR_BIN := \
 	pxar
 
 # Binaries usable by admins
-USR_SBIN := proxmox-backup-manager
+USR_SBIN := proxmox-backup-manager \
+	pbsbanner
 
 # Binaries for services:
 SERVICE_BIN := \

debian/proxmox-backup-server.install

@@ -1,8 +1,10 @@
 etc/proxmox-backup-proxy.service /lib/systemd/system/
 etc/proxmox-backup.service /lib/systemd/system/
+etc/pbsbanner.service /lib/systemd/system/
 usr/lib/x86_64-linux-gnu/proxmox-backup/proxmox-backup-api
 usr/lib/x86_64-linux-gnu/proxmox-backup/proxmox-backup-proxy
 usr/sbin/proxmox-backup-manager
+usr/sbin/pbsbanner
 usr/share/javascript/proxmox-backup/css/ext6-pbs.css
 usr/share/javascript/proxmox-backup/images/logo-128.png
 usr/share/javascript/proxmox-backup/images/proxmox_logo.png

etc/Makefile

@@ -1,13 +1,16 @@
 include ../defines.mk
 
 UNITS := \
+	pbsbanner.service \
+
+DYNAMIC_UNITS := \
 	proxmox-backup.service \
 	proxmox-backup-proxy.service
 
-all: $(UNITS)
+all: $(UNITS) $(DYNAMIC_UNITS)
 
 clean:
-	rm -f $(UNITS)
+	rm -f $(DYNAMIC_UNITS)
 
 .SUFFIXES: .service.in .service
 .service.in.service:

etc/pbsbanner.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=Proxmox Backup Server Login Banner
+ConditionPathExists=/usr/sbin/pbsbanner
+ConditionPathExists=!/usr/bin/pvebanner
+DefaultDependencies=no
+After=local-fs.target
+Before=console-getty.service
+
+[Service]
+ExecStart=/usr/sbin/pbsbanner
+Type=oneshot
+RemainAfterExit=yes
+
+[Install]
+WantedBy=getty.target

src/bin/pbsbanner.rs

@@ -0,0 +1,48 @@
+use std::fmt::Write;
+use std::fs;
+use std::net::ToSocketAddrs;
+
+use proxmox::tools;
+
+fn main() {
+    let nodename = tools::nodename();
+    let addr = format!("{}:8007", nodename);
+
+    let mut banner = format!("
+{:-<78}
+
+Welcome to the Proxmox Backup Server. Please use your web browser to
+configure this server - connect to:
+
+",
+        ""
+    );
+
+    if let Ok(saddrs) = addr.to_socket_addrs() {
+        let saddrs: Vec<_> = saddrs
+            .filter_map(|s| match !s.ip().is_loopback() {
+                true => Some(format!(" https://{}/", s)),
+                false => None,
+            })
+            .collect();
+
+        if !saddrs.is_empty() {
+            writeln!(&mut banner, "{}", saddrs.join("\n")).unwrap();
+        } else {
+            writeln!(
+                &mut banner,
+                "hostname '{}' does not resolves to any non-loopback address",
+                nodename
+            )
+            .unwrap();
+        }
+    } else {
+        writeln!(&mut banner, "could not resolve hostname '{}'", nodename).unwrap();
+    }
+
+    // unwrap will never fail for write!:
+    // https://github.com/rust-lang/rust/blob/1.39.0/src/liballoc/string.rs#L2318-L2331
+    write!(&mut banner, "\n{:-<78}\n\n", "").unwrap();
+
+    fs::write("/etc/issue", banner.as_bytes()).expect("Unable to write banner to issue file");
+}