rootfs: Get syslog servers from DHCP options

Instead of parsing the kernel command line to find the destination(s)
where syslog messages should be forwarded, we can use a *dhcpcd* hook to
get them from the DHCP lease.

cmdline.txt

@@ -1 +1 @@
-audit=0 panic=5 console=ttyAMA0 root=nbd:rosalina.pyrocufflink.blue:jenkinsagent rsyslog.dest=rosalina.pyrocufflink.blue sshkeys.root=http://rosalina.pyrocufflink.blue/~dustin/id_ed25519.pub
+audit=0 panic=5 console=ttyAMA0 root=nbd:rosalina.pyrocufflink.blue:jenkinsagent sshkeys.root=http://rosalina.pyrocufflink.blue/~dustin/id_ed25519.pub

rootfs/overlay/etc/dhcpcd.conf

@@ -39,6 +39,8 @@ option ntp_servers
 # on the server to actually work.
 option rapid_commit
 
+option log_servers
+
 # A ServerID is required by RFC2131.
 require dhcp_server_identifier
 

rootfs/overlay/usr/lib/dhcpcd/dhcpcd-hooks/60-syslog

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+gen_action() {
+    echo   'action('
+    echo   '    type="omfwd"'
+    printf '    Target="%s"\n' "${1}"
+    echo   '    Port="514"'
+    echo   '    template="RSYSLOG_SyslogProtocol23Format"'
+    echo   ')'
+}
+
+changed=false
+if [ -n "${interface}" ] && [ -d /run/rsyslog.d ]; then
+    if [ -n "${new_log_servers}" ]; then
+        echo '# Generated by dhcpcd' > /run/rsyslog.d/dhcpcd."${interface}".conf
+        for s in ${new_log_servers}; do
+            gen_action "${s}" >> /run/rsyslog.d/dhcpcd."${interface}".conf
+        done
+        changed=true
+    elif [ -n "${old_log_servers}" ]; then
+        rm -f /run/rsyslog.d/dhcpcd."${interface}".conf
+        changed=true
+    fi
+fi
+
+if ${changed}; then
+    systemctl try-restart rsyslog
+fi

rootfs/overlay/usr/lib/systemd/system/gen-rsyslog-conf.service

@@ -1,7 +0,0 @@
-[Unit]
-Description=Generate rsyslog.conf
-Before=rsyslog.service
-
-[Service]
-Type=oneshot
-ExecStart=/usr/libexec/gen-rsyslog-conf.sh

rootfs/overlay/usr/lib/systemd/system/rsyslog.service.d/after-network-online.conf

@@ -0,0 +1,2 @@
+[Unit]
+After=network-online.target

rootfs/overlay/usr/lib/systemd/system/rsyslog.service.wants/gen-rsyslog-conf.service

@@ -1 +0,0 @@
-../gen-rsyslog-conf.service

rootfs/overlay/usr/libexec/gen-rsyslog-conf.sh

@@ -1,12 +0,0 @@
-#!/bin/sh -e
-
-# shellcheck disable=SC2046
-set -- $(cat /proc/cmdline)
-while [ $# -ge 1 ]; do
-    case "$1" in
-    rsyslog.dest=*)
-        printf '*.* @%s\n' "${1#*=}" >> /run/rsyslog.d/remote.conf
-        ;;
-    esac
-    shift
-done