updating dns override

dns-override.sh

@@ -3,7 +3,8 @@
 set -euo pipefail
 
 readonly SCRIPT_NAME="dns-override.sh"
-readonly SCRIPT_VERSION="1.0.0"
+readonly SCRIPT_VERSION="1.0.2"
+readonly IMMUTABLE_PROMPT_TIMEOUT_SEC=20
 
 readonly NC='\033[0m'
 readonly RED='\033[1;31m'
@@ -22,6 +23,8 @@ readonly EMOJI_NET='🌐'
 readonly EMOJI_LOCK='🔒'
 
 SUDO_BIN=""
+IS_REMOTE_SSH=0
+IMMUTABLE_LOCK_REQUESTED=0
 declare -a DNS_SERVERS=()
 declare -a DETECTED_MANAGERS=()
 declare -a ACTIONS_ATTEMPTED=()
@@ -44,6 +47,27 @@ command_exists() {
   command -v "$1" >/dev/null 2>&1
 }
 
+binary_or_path_exists() {
+  local bin_name="$1"
+  shift
+
+  if command_exists "$bin_name"; then
+    return 0
+  fi
+
+  local path_candidate
+  for path_candidate in "$@"; do
+    [[ -x "$path_candidate" ]] && return 0
+  done
+  return 1
+}
+
+systemd_unit_exists() {
+  local unit_name="$1"
+  command_exists systemctl || return 1
+  systemctl list-unit-files "$unit_name" >/dev/null 2>&1
+}
+
 trim() {
   local value="$1"
   value="${value#"${value%%[![:space:]]*}"}"
@@ -98,6 +122,15 @@ read_tty_input() {
   printf '%s' "$(trim "$value")"
 }
 
+read_tty_input_timeout() {
+  local prompt="$1"
+  local timeout_sec="$2"
+  local value
+  printf "%b" "$prompt" >/dev/tty
+  IFS= read -r -t "$timeout_sec" value </dev/tty || return $?
+  printf '%s' "$(trim "$value")"
+}
+
 run_root() {
   if [[ -n "$SUDO_BIN" ]]; then
     "$SUDO_BIN" "$@"
@@ -144,6 +177,49 @@ ensure_root_context() {
   SUDO_BIN="sudo"
 }
 
+detect_runtime_context() {
+  if [[ -n "${SSH_CONNECTION:-}" || -n "${SSH_TTY:-}" ]]; then
+    IS_REMOTE_SSH=1
+    log_warning "SSH session detected. Using safer apply behavior to reduce connection drops."
+  fi
+}
+
+has_systemd_resolved() {
+  binary_or_path_exists "resolvectl" "/usr/bin/resolvectl" "/bin/resolvectl" && return 0
+  systemd_unit_exists "systemd-resolved.service" && return 0
+  binary_or_path_exists "systemd-resolved" "/lib/systemd/systemd-resolved" "/usr/lib/systemd/systemd-resolved" && return 0
+  return 1
+}
+
+has_networkmanager() {
+  binary_or_path_exists "nmcli" "/usr/bin/nmcli" "/bin/nmcli" && return 0
+  binary_or_path_exists "NetworkManager" "/usr/sbin/NetworkManager" "/sbin/NetworkManager" && return 0
+  systemd_unit_exists "NetworkManager.service" && return 0
+  return 1
+}
+
+has_resolvconf_openresolv() {
+  binary_or_path_exists "resolvconf" "/sbin/resolvconf" "/usr/sbin/resolvconf" && return 0
+  return 1
+}
+
+has_dhclient() {
+  binary_or_path_exists "dhclient" "/sbin/dhclient" "/usr/sbin/dhclient" && return 0
+  return 1
+}
+
+has_systemd_networkd() {
+  systemd_unit_exists "systemd-networkd.service" && return 0
+  binary_or_path_exists "systemd-networkd" "/lib/systemd/systemd-networkd" "/usr/lib/systemd/systemd-networkd" && return 0
+  return 1
+}
+
+has_ifupdown() {
+  binary_or_path_exists "ifup" "/sbin/ifup" "/usr/sbin/ifup" && return 0
+  [[ -f /etc/network/interfaces || -d /etc/network/interfaces.d ]] && return 0
+  return 1
+}
+
 add_manager() {
   local manager="$1"
   if ! contains_value "$manager" "${DETECTED_MANAGERS[@]}"; then
@@ -154,31 +230,27 @@ add_manager() {
 detect_managers() {
   DETECTED_MANAGERS=()
 
-  if command_exists systemctl && systemctl is-active --quiet systemd-resolved 2>/dev/null; then
-    add_manager "systemd-resolved"
-  elif [[ -L /etc/resolv.conf ]] && readlink /etc/resolv.conf 2>/dev/null | grep -Eq 'systemd/resolve'; then
+  if has_systemd_resolved; then
     add_manager "systemd-resolved"
   fi
 
-  if command_exists nmcli || [[ -d /etc/NetworkManager ]]; then
+  if has_networkmanager; then
     add_manager "NetworkManager"
   fi
 
-  if command_exists resolvconf || [[ -d /etc/resolvconf ]] || [[ -f /etc/resolvconf.conf ]]; then
+  if has_resolvconf_openresolv; then
     add_manager "resolvconf/openresolv"
   fi
 
-  if command_exists dhclient || [[ -f /etc/dhcp/dhclient.conf ]]; then
+  if has_dhclient; then
     add_manager "dhclient"
   fi
 
-  if command_exists systemctl && systemctl is-active --quiet systemd-networkd 2>/dev/null; then
-    add_manager "systemd-networkd"
-  elif [[ -d /etc/systemd/network ]]; then
+  if has_systemd_networkd; then
     add_manager "systemd-networkd"
   fi
 
-  if [[ -f /etc/network/interfaces ]] || [[ -d /etc/network/interfaces.d ]]; then
+  if has_ifupdown; then
     add_manager "ifupdown"
   fi
 }
@@ -336,7 +408,7 @@ run_action() {
   rc=$?
   if [[ "$rc" -eq 2 ]]; then
     ACTIONS_SKIPPED+=("$action")
-    log_info "$action not applicable on this system"
+    log_info "$action skipped: target manager is not present on this host"
     return 0
   fi
 
@@ -374,7 +446,8 @@ apply_static_resolv_conf() {
 }
 
 apply_systemd_resolved() {
-  if ! command_exists systemctl && ! command_exists resolvectl && [[ ! -d /etc/systemd ]]; then
+  if ! has_systemd_resolved; then
+    log_info "Skipping systemd-resolved override: systemd-resolved is not present."
     return 2
   fi
 
@@ -409,7 +482,8 @@ apply_systemd_resolved() {
 }
 
 apply_networkmanager() {
-  if ! command_exists nmcli && [[ ! -d /etc/NetworkManager ]]; then
+  if ! has_networkmanager; then
+    log_info "Skipping NetworkManager override: NetworkManager is not present."
     return 2
   fi
 
@@ -430,21 +504,37 @@ apply_networkmanager() {
       run_root nmcli connection modify "$conn" ipv6.ignore-auto-dns yes >/dev/null 2>&1 || true
       run_root nmcli connection modify "$conn" ipv4.dns "$dns_csv" >/dev/null 2>&1 || true
       run_root nmcli connection modify "$conn" ipv6.dns "$dns_csv" >/dev/null 2>&1 || true
-      run_root nmcli connection up "$conn" >/dev/null 2>&1 || true
     done < <(nmcli -g NAME connection show --active 2>/dev/null || true)
 
+    run_root nmcli connection reload >/dev/null 2>&1 || true
+
+    if [[ "$IS_REMOTE_SSH" -eq 1 ]]; then
+      log_warning "Skipping NetworkManager reconnect/restart operations in SSH session."
+      local dev
+      while IFS= read -r dev; do
+        [[ -n "$dev" && "$dev" != "lo" ]] || continue
+        run_root nmcli device reapply "$dev" >/dev/null 2>&1 || true
+      done < <(nmcli -t -f DEVICE,STATE device status 2>/dev/null | awk -F: '$2=="connected" || $2=="connecting" {print $1}')
+    else
+      while IFS= read -r conn; do
+        [[ -n "$conn" ]] || continue
+        run_root nmcli connection up "$conn" >/dev/null 2>&1 || true
+      done < <(nmcli -g NAME connection show --active 2>/dev/null || true)
+    fi
+
     run_root nmcli general reload >/dev/null 2>&1 || true
   fi
 
   if command_exists systemctl; then
-    run_root systemctl reload NetworkManager >/dev/null 2>&1 || run_root systemctl restart NetworkManager >/dev/null 2>&1 || true
+    run_root systemctl reload NetworkManager >/dev/null 2>&1 || true
   fi
 
   return 0
 }
 
 apply_resolvconf_openresolv() {
-  if ! command_exists resolvconf && [[ ! -d /etc/resolvconf ]] && [[ ! -f /etc/resolvconf.conf ]]; then
+  if ! has_resolvconf_openresolv; then
+    log_info "Skipping resolvconf/openresolv override: resolvconf/openresolv is not present."
     return 2
   fi
 
@@ -464,7 +554,8 @@ apply_resolvconf_openresolv() {
 }
 
 apply_dhclient() {
-  if ! command_exists dhclient && [[ ! -f /etc/dhcp/dhclient.conf ]] && [[ ! -d /etc/dhcp ]]; then
+  if ! has_dhclient; then
+    log_info "Skipping dhclient override: dhclient is not present."
     return 2
   fi
 
@@ -485,7 +576,8 @@ apply_dhclient() {
 }
 
 apply_systemd_networkd() {
-  if ! command_exists systemctl && [[ ! -d /etc/systemd/network ]]; then
+  if ! has_systemd_networkd; then
+    log_info "Skipping systemd-networkd override: systemd-networkd is not present."
     return 2
   fi
 
@@ -515,7 +607,18 @@ apply_systemd_networkd() {
 
   if command_exists systemctl; then
     run_root systemctl daemon-reload >/dev/null 2>&1 || true
-    run_root systemctl restart systemd-networkd >/dev/null 2>&1 || run_root systemctl try-restart systemd-networkd >/dev/null 2>&1 || true
+    if command_exists networkctl; then
+      run_root networkctl reload >/dev/null 2>&1 || true
+      if [[ "$IS_REMOTE_SSH" -eq 0 ]]; then
+        run_root networkctl reconfigure --all >/dev/null 2>&1 || true
+      else
+        log_warning "Skipping networkctl reconfigure --all in SSH session."
+      fi
+    elif [[ "$IS_REMOTE_SSH" -eq 0 ]]; then
+      run_root systemctl restart systemd-networkd >/dev/null 2>&1 || run_root systemctl try-restart systemd-networkd >/dev/null 2>&1 || true
+    else
+      log_warning "Skipping systemd-networkd restart in SSH session."
+    fi
   fi
 
   return 0
@@ -567,7 +670,8 @@ patch_ifupdown_file() {
 }
 
 apply_ifupdown() {
-  if [[ ! -f /etc/network/interfaces ]] && [[ ! -d /etc/network/interfaces.d ]]; then
+  if ! has_ifupdown; then
+    log_info "Skipping ifupdown override: ifupdown is not present."
     return 2
   fi
 
@@ -611,22 +715,41 @@ prompt_immutable_lock() {
   }
 
   local answer
-  answer="$(read_tty_input "${YELLOW}${EMOJI_LOCK} Make /etc/resolv.conf immutable with chattr +i? [y/N]: ${NC}")" || return 1
+  if ! answer="$(read_tty_input_timeout "${YELLOW}${EMOJI_LOCK} Make /etc/resolv.conf immutable with chattr +i? [y/N] (auto No in ${IMMUTABLE_PROMPT_TIMEOUT_SEC}s): ${NC}" "$IMMUTABLE_PROMPT_TIMEOUT_SEC")"; then
+    local rc=$?
+    if [[ "$rc" -gt 128 ]]; then
+      log_warning "No response received for immutable lock prompt; defaulting to No."
+      IMMUTABLE_LOCK_REQUESTED=0
+      return 0
+    fi
+    return 1
+  fi
+
   case "$answer" in
     y|Y|yes|YES)
-      if run_root chattr +i /etc/resolv.conf; then
-        log_success "Immutable lock applied to /etc/resolv.conf."
-        log_warning "To edit DNS later, run: sudo chattr -i /etc/resolv.conf"
-      else
-        log_warning "Failed to apply immutable lock."
-      fi
+      IMMUTABLE_LOCK_REQUESTED=1
+      log_info "Immutable lock requested. It will be applied after DNS updates."
       ;;
     *)
+      IMMUTABLE_LOCK_REQUESTED=0
       log_info "Immutable lock skipped."
       ;;
   esac
 }
 
+apply_immutable_lock_if_requested() {
+  if [[ "$IMMUTABLE_LOCK_REQUESTED" -ne 1 ]]; then
+    return 0
+  fi
+
+  if run_root chattr +i /etc/resolv.conf; then
+    log_success "Immutable lock applied to /etc/resolv.conf."
+    log_warning "To edit DNS later, run: sudo chattr -i /etc/resolv.conf"
+  else
+    log_warning "Failed to apply immutable lock."
+  fi
+}
+
 print_summary() {
   echo
   log_step "Execution summary"
@@ -669,7 +792,9 @@ main() {
 
   require_tty
   ensure_root_context "$@"
+  detect_runtime_context
   prompt_dns_servers
+  prompt_immutable_lock || log_warning "Immutable lock prompt failed; defaulting to unlocked."
   run_connectivity_checks
   detect_managers
 
@@ -681,7 +806,7 @@ main() {
   run_action "Apply ifupdown override" apply_ifupdown
   run_action "Write /etc/resolv.conf directly" apply_static_resolv_conf
 
-  prompt_immutable_lock || log_warning "Immutable lock prompt failed; continuing."
+  run_action "Apply immutable /etc/resolv.conf lock (if requested)" apply_immutable_lock_if_requested
   print_summary
 
   echo