Add port forwarding: local, remote and dynamic, per terminal session

A host can now carry port forwards (-L, -R, -D), saved inside its
encrypted payload as RelayTicketRequest.PortForwardId already assumed,
so they sync and merge per forward like tags and pinned paths. The host
schema moves to version 8 only for hosts that carry forwards.

ISshConnection gains StartForwardAsync over SSH.NET's forwarded ports.
Every listener binds loopback and there is no bind-address field: a
forward is something any member of a shared keychain can edit. A remote
forward's target is resolved here, IPv4 first, rather than by SSH.NET's
constructor, which takes the first DNS answer and can send ::1.

Forwards start with every terminal opened to the host and stop with its
connection; a reconnect starts them again. The session sidebar lists
them with state, failure reason and an on/off switch, the status bar
counts the listening ones, and the host editor and detail pane gain a
PORT FORWARDS section. A forward that cannot start fails alone.

The phone does not start forwards yet: it has no surface showing what
is listening, and its More screen now says so. No byte counts, since
SSH.NET keeps none.

src/DodoSSH.Client.App/Views/HostDrawer.axaml

@@ -1,6 +1,7 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:vm="using:DodoSSH.Client.Shell.ViewModels"
+             xmlns:dom="using:DodoSSH.Client.Domain"
              xmlns:views="using:DodoSSH.Client.App.Views"
              x:Class="DodoSSH.Client.App.Views.HostDrawer"
              x:DataType="vm:VaultViewModel">
@@ -385,6 +386,33 @@
               </StackPanel>
             </Border>
 
+            <!--
+              ============ FORWARDS (read-only) ============
+              QUICK ACCESS's shape, and hidden when empty for the same reason: a card with nothing under it
+              answers a question nobody asked here.
+            -->
+            <Border Classes="section" IsVisible="{Binding SelectedHost.HasForwards}">
+              <StackPanel Spacing="6">
+                <TextBlock Classes="sectionhead" Text="Port forwards" Margin="0,0,0,2" />
+
+                <Button Classes="fieldrow" Command="{Binding EditSelectedHostCommand}">
+                  <Grid ColumnDefinitions="Auto,*">
+                    <TextBlock Grid.Column="0" FontFamily="{StaticResource IconFont}" FontSize="13"
+                               Foreground="{StaticResource TextFaint}" Width="16" VerticalAlignment="Top"
+                               Margin="0,3,0,0" Text="&#xE8D4;" />
+                    <ItemsControl Grid.Column="1" ItemsSource="{Binding SelectedHost.Host.PortForwards}">
+                      <ItemsControl.ItemTemplate>
+                        <DataTemplate x:DataType="dom:PortForwardRule">
+                          <TextBlock Classes="mono" Text="{Binding Notation}" FontSize="12"
+                                     TextTrimming="CharacterEllipsis" Margin="0,0,0,2" />
+                        </DataTemplate>
+                      </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+                  </Grid>
+                </Button>
+              </StackPanel>
+            </Border>
+
             <TextBlock Classes="hint" FontSize="11" TextWrapping="Wrap"
                        Text="Double-clicking the card does the same as CONNECT. The terminal opens as a tab in the strip above and stays there while you look at anything else." />
 
@@ -740,6 +768,84 @@
               </StackPanel>
             </Border>
 
+            <!--
+              ============ PORT FORWARDS ============
+              Staged on VaultViewModel.EditorPortForwards the way QUICK ACCESS stages its pins, and saved
+              with the host. Each row is drawn in OpenSSH's own notation, because that is what anybody who has
+              used one reads fastest; the add row spells out which end the listening port is on instead,
+              because -L and -R are the two flags people get backwards.
+
+              No bind-address field, and that is not an omission: every listener binds loopback. A forward is
+              a field every member of a shared keychain can fill in, and one bound to 0.0.0.0 would hand the
+              remote's network to anybody who can reach this machine. See SshPortForwardSpec.
+            -->
+            <Border Classes="section">
+              <StackPanel Spacing="8">
+                <TextBlock Classes="sectionlabel" Text="PORT FORWARDS" />
+
+                <ItemsControl ItemsSource="{Binding EditorPortForwards}">
+                  <ItemsControl.ItemsPanel>
+                    <ItemsPanelTemplate><StackPanel Spacing="6" /></ItemsPanelTemplate>
+                  </ItemsControl.ItemsPanel>
+                  <ItemsControl.ItemTemplate>
+                    <DataTemplate x:DataType="dom:PortForwardRule">
+                      <Border Height="33" CornerRadius="9" Background="{StaticResource Field}"
+                              BorderBrush="{StaticResource Border}" BorderThickness="1" Padding="8,0">
+                        <Grid ColumnDefinitions="Auto,*,Auto">
+                          <TextBlock Grid.Column="0" FontFamily="{StaticResource IconFont}" FontSize="14"
+                                     Foreground="{StaticResource TextFaint}" VerticalAlignment="Center"
+                                     Text="&#xE8D4;" />
+                          <TextBlock Grid.Column="1" Classes="mono" Text="{Binding Notation}" FontSize="12.5"
+                                     Margin="8,0" VerticalAlignment="Center"
+                                     TextTrimming="CharacterEllipsis" ToolTip.Tip="{Binding Notation}" />
+                          <Button Grid.Column="2" Classes="flat paneicon" Content="✕" Width="22" Height="22"
+                                  FontSize="11"
+                                  Command="{Binding $parent[ItemsControl].((vm:VaultViewModel)DataContext).RemoveEditorForwardCommand}"
+                                  CommandParameter="{Binding}" ToolTip.Tip="Removes this forward" />
+                        </Grid>
+                      </Border>
+                    </DataTemplate>
+                  </ItemsControl.ItemTemplate>
+                </ItemsControl>
+
+                <ComboBox SelectedIndex="{Binding EditorNewForwardKind}" HorizontalAlignment="Stretch"
+                          Height="36">
+                  <ComboBoxItem Content="Local  -L" />
+                  <ComboBoxItem Content="Remote  -R" />
+                  <ComboBoxItem Content="Dynamic  -D  (SOCKS)" />
+                </ComboBox>
+
+                <!-- Which end each port is on, for the kind chosen: the thing -L and -R get backwards. -->
+                <TextBlock Classes="hint" FontSize="11" TextWrapping="Wrap"
+                           Text="{Binding EditorNewForwardKindHint}" />
+
+                <Grid ColumnDefinitions="104,6,*,6,Auto">
+                  <TextBox Grid.Column="0" FontFamily="{StaticResource MonoFont}"
+                           Text="{Binding EditorNewForwardBindPort}"
+                           PlaceholderText="{Binding EditorNewForwardBindHint}" Height="36"
+                           ToolTip.Tip="{Binding EditorNewForwardBindHint}">
+                    <TextBox.KeyBindings>
+                      <KeyBinding Gesture="Enter" Command="{Binding AddEditorForwardCommand}" />
+                    </TextBox.KeyBindings>
+                  </TextBox>
+                  <TextBox Grid.Column="2" FontFamily="{StaticResource MonoFont}"
+                           Text="{Binding EditorNewForwardTarget}"
+                           IsVisible="{Binding EditorNewForwardHasTarget}"
+                           PlaceholderText="host:port" Height="36">
+                    <TextBox.KeyBindings>
+                      <KeyBinding Gesture="Enter" Command="{Binding AddEditorForwardCommand}" />
+                    </TextBox.KeyBindings>
+                  </TextBox>
+                  <Button Grid.Column="4" Classes="ghost" Content="+" Width="36" Height="36" FontSize="15"
+                          HorizontalContentAlignment="Center"
+                          Command="{Binding AddEditorForwardCommand}" ToolTip.Tip="Adds this forward" />
+                </Grid>
+
+                <TextBlock Classes="hint" FontSize="11.5" TextWrapping="Wrap"
+                           Text="Forwards start with every terminal opened to this host and stop when it closes. Everything listens on localhost only. A change here applies from the next connection." />
+              </StackPanel>
+            </Border>
+
           </StackPanel>
 
           <!-- ============ THE GROUP EDITOR ============ -->

src/DodoSSH.Client.App/Views/MainWindow.axaml

@@ -332,7 +332,7 @@
                   a sidebar naming no host would be furniture with nothing to say. Collapsing frees the
                   "Auto" column it sits in, so the pane column takes the width back.
                 -->
-                <views:SessionSidebar Grid.Column="1" ShowsSnips="True"
+                <views:SessionSidebar Grid.Column="1" ShowsSnips="True" ShowsForwards="True"
                                       IsVisible="{Binding ShowsQuickAccessSidebar, FallbackValue=False}" />
               </Grid>
             </Border>

src/DodoSSH.Client.App/Views/SessionSidebar.axaml

@@ -39,6 +39,22 @@
     is showing without knowing anything about the state — and the pane beside it grows into what is freed.
   -->
 
+  <!--
+    A forward's state word: green only while it is listening, which is the one status Live is for, and the
+    danger text colour for a forward that could not start. OFF and STARTING stay faint.
+  -->
+  <UserControl.Styles>
+    <Style Selector="TextBlock.fwdstate">
+      <Setter Property="Foreground" Value="{StaticResource TextFaint}" />
+    </Style>
+    <Style Selector="TextBlock.fwdstate.live">
+      <Setter Property="Foreground" Value="{StaticResource Live}" />
+    </Style>
+    <Style Selector="TextBlock.fwdstate.failed">
+      <Setter Property="Foreground" Value="{StaticResource DangerText}" />
+    </Style>
+  </UserControl.Styles>
+
   <Panel>
 
     <!-- ============ THE RAIL, WHEN THE COLUMN IS CLOSED ============ -->
@@ -142,6 +158,64 @@
             </StackPanel>
           </Button>
 
+          <!-- ============ FORWARDS (the terminal surface only) ============ -->
+          <!--
+            The selected tab's forwards: the host's saved ones, as they run over this session. Each row is
+            its own switch, and a failed one says why under its notation — a port already taken, most often
+            by a second tab to the same host running the same forwards. Nothing here edits a forward; the add
+            row goes to the host's editor, where they are saved, as Pin folder does for QUICK ACCESS.
+
+            No byte counts, which the design draws. SSH.NET keeps no count of what a forward carries, so a
+            number here would be invented.
+          -->
+          <StackPanel Spacing="6" Margin="0,16,0,0" IsVisible="{Binding #Root.ShowsForwards}">
+
+            <TextBlock Classes="label" Text="FORWARDS" FontSize="10" Margin="8,0" />
+
+            <ItemsControl ItemsSource="{Binding SelectedTab.Forwards}">
+              <ItemsControl.ItemTemplate>
+                <DataTemplate x:DataType="vm:PortForwardViewModel">
+                  <!--
+                    The reason sits under the row rather than inside it: a sidebar row is a fixed 33 pixels, and
+                    a refusal is a sentence. Indented to the notation, so it reads as belonging to the row.
+                  -->
+                  <StackPanel>
+                    <Button Classes="sidebarrow" Command="{Binding ToggleCommand}"
+                            ToolTip.Tip="{Binding Route}">
+                      <Grid ColumnDefinitions="Auto,*,Auto">
+                        <TextBlock Grid.Column="0" Text="&#xE8D4;"
+                                   FontFamily="{StaticResource IconFont}" FontSize="15"
+                                   Foreground="{StaticResource AccentText}" VerticalAlignment="Center"
+                                   Margin="0,0,10,0" />
+                        <TextBlock Grid.Column="1" FontFamily="{StaticResource MonoFont}" FontSize="12.5"
+                                   Text="{Binding Notation}" TextTrimming="CharacterEllipsis"
+                                   VerticalAlignment="Center" />
+                        <TextBlock Grid.Column="2" Classes="fwdstate" FontFamily="Montserrat"
+                                   FontWeight="SemiBold" FontSize="9" LetterSpacing="1"
+                                   VerticalAlignment="Center" Margin="8,0,0,0"
+                                   Text="{Binding StateText}"
+                                   Classes.live="{Binding IsListening}" Classes.failed="{Binding IsFailed}" />
+                      </Grid>
+                    </Button>
+                    <TextBlock FontSize="11" Foreground="{StaticResource TextFaint}" TextWrapping="Wrap"
+                               Margin="37,0,12,4" Text="{Binding Detail}"
+                               IsVisible="{Binding Detail, Converter={x:Static StringConverters.IsNotNullOrEmpty}}" />
+                  </StackPanel>
+                </DataTemplate>
+              </ItemsControl.ItemTemplate>
+            </ItemsControl>
+
+            <Button Classes="sidebaradd" Command="{Binding AddForwardFromSidebarCommand}"
+                    ToolTip.Tip="Opens the active tab's host for editing, where its forwards are saved. A new forward starts with the next connection.">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Text="&#xE145;" FontFamily="{StaticResource IconFont}" FontSize="14"
+                           VerticalAlignment="Center" />
+                <TextBlock Text="Add forward" VerticalAlignment="Center" />
+              </StackPanel>
+            </Button>
+
+          </StackPanel>
+
           <!-- ============ SNIPS (the terminal surface only) ============ -->
           <StackPanel Spacing="6" Margin="0,16,0,0" IsVisible="{Binding #Root.ShowsSnips}">
 

src/DodoSSH.Client.App/Views/SessionSidebar.axaml.cs

@@ -19,6 +19,10 @@ internal sealed partial class SessionSidebar : UserControl
     internal static readonly StyledProperty<bool> ShowsSnipsProperty =
         AvaloniaProperty.Register<SessionSidebar, bool>(nameof(ShowsSnips));
 
+    /// <summary>Whether the FORWARDS section draws. The terminal's own, for the reason SNIPS is.</summary>
+    internal static readonly StyledProperty<bool> ShowsForwardsProperty =
+        AvaloniaProperty.Register<SessionSidebar, bool>(nameof(ShowsForwards));
+
     public SessionSidebar() => InitializeComponent();
 
     internal bool ShowsSnips
@@ -26,4 +30,10 @@ internal sealed partial class SessionSidebar : UserControl
         get => GetValue(ShowsSnipsProperty);
         set => SetValue(ShowsSnipsProperty, value);
     }
+
+    internal bool ShowsForwards
+    {
+        get => GetValue(ShowsForwardsProperty);
+        set => SetValue(ShowsForwardsProperty, value);
+    }
 }

src/DodoSSH.Client.App/Views/SessionStatusBar.axaml

@@ -76,6 +76,13 @@
       </StackPanel>
 
       <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="18" VerticalAlignment="Center">
+        <!--
+          How many of the selected tab's forwards are listening, and nothing when none are. The terminal's
+          own, for the reason UTF-8 is: an SFTP connection runs no forwards.
+        -->
+        <TextBlock Classes="mono" FontSize="11.5" Foreground="{StaticResource TextGhost}"
+                   VerticalAlignment="Center" Text="{Binding SelectedTab.ForwardsSummary}"
+                   IsVisible="{Binding #Root.ShowsEncoding}" />
         <TextBlock Classes="mono" FontSize="11.5" Foreground="{StaticResource TextGhost}"
                    VerticalAlignment="Center" Text="{Binding SessionElapsedText}"
                    IsVisible="{Binding SessionElapsedText, Converter={x:Static StringConverters.IsNotNullOrEmpty}}" />

src/DodoSSH.Client.App/Views/StatusBar.axaml

@@ -9,8 +9,9 @@
 
     The design puts five things here: the active host and the bastion it is reached through, the open port
     forwards, the SFTP transfer count, an auto-lock countdown, and the last sync time. Four of those five
-    have nothing behind them — there is no jump-host routing, no port forwarding, no file transfer and no
-    idle auto-lock — so what is left is the active session, the vault's last message, and the shortcut hint.
+    had nothing behind them when this was written — there was no jump-host routing, no port forwarding, no
+    file transfer and no idle auto-lock — so what is left is the active session, the vault's last message,
+    and the shortcut hint. Forwards have since been built, and are counted on SessionStatusBar instead.
 
     The last message is the load-bearing one, and it is why this bar is worth having at all: the vault's
     status line used to be a cramped label in the account bar, and everything the application has to say