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Robby Zambito
2026-01-19 12:27:24 -05:00
parent 9947c21b4c
commit d7dedd243e
1 changed files with 60 additions and 36 deletions
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96
src/main.zig
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@@ -99,36 +99,40 @@ pub fn main(init: std.process.Init) !void {
// std.debug.print("Interface: {s}\n", .{(try net_interface.name(init.io)).toSlice()});
const EthIpUdp = packed struct(u336) { // 42 bytes * 8 bits = 336
// --- UDP (Last in memory, defined first for LSB->MSB) ---
checksum: u16 = 0,
udp_len: u16,
dst_port: u16,
src_port: u16,
udp: packed struct {
checksum: u16 = 0,
len: u16,
dst_port: u16,
src_port: u16,
},
// --- IP ---
dst_addr: u32,
src_addr: u32,
header_checksum: u16 = 0,
protocol: u8 = 17, // udp
ttl: u8 = 0x40,
ip: packed struct {
dst_addr: u32,
src_addr: u32,
header_checksum: u16 = 0,
protocol: u8 = 17, // udp
ttl: u8 = 0x40,
// fragment_offset (13 bits) + flags (3 bits) = 16 bits
// In Big Endian, flags are the high bits of the first byte.
// To have flags appear first in the stream, define them last here.
fragment_offset: u13 = 0,
flags: packed struct(u3) {
reserved: u1 = 0,
dont_fragment: u1 = 0,
more_fragments: u1 = 0,
} = .{},
// fragment_offset (13 bits) + flags (3 bits) = 16 bits
// In Big Endian, flags are the high bits of the first byte.
// To have flags appear first in the stream, define them last here.
fragment_offset: u13 = 0,
flags: packed struct(u3) {
reserved: u1 = 0,
dont_fragment: u1 = 0,
more_fragments: u1 = 0,
} = .{},
id: u16,
total_length: u16,
tos: u8 = undefined,
id: u16,
len: u16,
tos: u8 = undefined,
// ip_version (4 bits) + ihl (4 bits) = 8 bits
// To have version appear first (high nibble), define it last.
ihl: u4 = 5,
ip_version: u4 = 4,
// ip_version (4 bits) + ihl (4 bits) = 8 bits
// To have version appear first (high nibble), define it last.
ihl: u4 = 5,
ip_version: u4 = 4,
},
// --- Ethernet ---
eth_type: u16 = std.os.linux.ETH.P.IP,
@@ -141,18 +145,26 @@ pub fn main(init: std.process.Init) !void {
w.writeStruct(self, .big) catch unreachable;
return res;
}
fn setPayloadLen(self: *@This(), len: usize) void {
self.ip.len = @intCast(len + @sizeOf(@TypeOf(self.udp)) + @sizeOf(@TypeOf(self.ip)));
self.udp.len = @intCast(len + @sizeOf(@TypeOf(self.udp)));
}
};
const headers: EthIpUdp = .{
var headers: EthIpUdp = .{
.src_mac = @splat(0x0e),
.id = 0,
.src_addr = 0,
.dst_addr = @bitCast([_]u8{ 255, 255, 255, 255 }),
.src_port = undefined, // TODO: change this?
.dst_port = 8888,
.total_length = undefined,
.udp_len = undefined,
.ip = .{
.id = 0,
.src_addr = 0,
.dst_addr = @bitCast([_]u8{ 255, 255, 255, 255 }),
.len = undefined,
},
.udp = .{
.src_port = undefined, // TODO: change this?
.dst_port = 8888,
.len = undefined,
},
};
std.debug.print("headers: {any}\n", .{&headers.toBytes()});
@@ -163,8 +175,20 @@ pub fn main(init: std.process.Init) !void {
},
};
var relay_bytes: [2048]u8 = undefined;
std.debug.print("payload: {any}\n", .{relay.toBytes(&relay_bytes)});
var relay_buf: [2048]u8 = undefined;
const relay_bytes = relay.toBytes(&relay_buf);
std.debug.print("payload: {any}\n", .{relay_bytes});
headers.setPayloadLen(relay_bytes.len);
const full_msg = blk: {
var msg_buf: [2048]u8 = undefined;
var msg_w: Writer = .fixed(&msg_buf);
msg_w.writeAll(&headers.toBytes()) catch unreachable;
msg_w.writeAll(relay_bytes) catch unreachable;
break :blk msg_w.buffered();
};
std.debug.print("full message = {any}\n", .{full_msg});
}
fn parseDest(in: ?[]const u8) [4]u8 {