Initial commit

.gitignore

@@ -0,0 +1 @@
+.idea

Dockerfile

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+FROM golang:latest
+
+WORKDIR /usr/src/little-stitch
+ENV GO11MODULES on
+RUN apt-get update && apt-get install -y \
+    libpcap-dev \
+    iproute2
+COPY ./go.mod ./go.sum ./*.go ./
+RUN go build -o /usr/local/bin/little-stitch ./main.go
+ENTRYPOINT ["/usr/local/bin/little-stitch"]

go.mod

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+module github.com/RyanJarv/little-stitch
+
+go 1.17

lib/send.go

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+package lib
+
+import (
+	"fmt"
+	"io"
+	"syscall"
+	"time"
+)
+
+const TIMEOUT = time.Second
+const BASE_PORT = 60000
+
+func NewConnection(addr [4]byte) *io.PipeWriter {
+	r, w := io.Pipe()
+	go connection(addr, r)
+	return w
+}
+
+func connection(addr [4]byte, in *io.PipeReader) error {
+	for {
+		var b []byte
+		_, err := in.Read(b)
+		if err != nil {
+			return err
+		}
+
+		// Send clock ping, notifies the server we are starting the next byte.
+		_, err = Ping(&syscall.SockaddrInet4{Addr: addr, Port: BASE_PORT})
+		if err != nil {
+			fmt.Printf("[ERROR] Recieved error when sending clock ping: %s\n", err)
+		}
+		for _, b := range b {
+			for i := 1; i <= 8; i++ {
+				err := sendBit(addr, b, i)
+				if err != nil {
+					fmt.Printf("[ERROR] Recieved error when sending bit %d: %s\n", i, err)
+				}
+			}
+		}
+	}
+}
+
+func sendBit(addr [4]byte, b byte, bit int) error {
+	if (int(b) & bit) == 1 {
+		_, err := Ping(&syscall.SockaddrInet4{Addr: addr, Port: BASE_PORT + bit})
+		return err
+	}
+	return nil
+}
+
+func Ping(addr syscall.Sockaddr) (bool, error) {
+	sock, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
+	if err != nil {
+		return false, fmt.Errorf("creating socket: %w\n", err)
+	}
+	defer func(sock int) {
+		err := syscall.Close(sock)
+		if err != nil {
+			fmt.Printf("Failed to close socket %d\n", sock)
+		}
+	}(sock)
+
+	//fmt.Println("socket resp: ", sock)
+
+	err = syscall.Connect(sock, addr)
+	for err == syscall.EINTR {
+		err = syscall.Connect(sock, addr)
+	}
+
+	start := time.Now()
+	_, err = syscall.Getpeername(sock)
+
+	for err != nil {
+		if err.Error() == "invalid argument" {
+			return false, fmt.Errorf("connection rejected")
+		} else if time.Now().After(start.Add(TIMEOUT)) {
+			return false, fmt.Errorf("connection timedout")
+		} else if err.Error() == "socket is not connected" {
+			time.Sleep(TIMEOUT / 20)
+			_, err = syscall.Getpeername(sock)
+		}
+	}
+	return true, nil
+}

lib/send_test.go

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+package lib
+
+import (
+	"syscall"
+	"testing"
+)
+
+func TestPing(t *testing.T) {
+	type args struct {
+		addr syscall.Sockaddr
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    bool
+		wantErr bool
+	}{
+		{
+			"returns true and no error when ran against a open port",
+			args{
+				&syscall.SockaddrInet4{
+					Port: 80,
+					Addr: [4]byte{1,1,1,1},
+				},
+			},
+			true,
+			false,
+		},
+		{
+			"returns false and an error when ran against a filtered port",
+			args{
+				&syscall.SockaddrInet4{
+					Port: 1234,
+					Addr: [4]byte{1,1,1,1},
+				},
+			},
+			true,
+			false,
+		},
+		{
+			"returns false and an error when ran against a closed port",
+			args{
+				&syscall.SockaddrInet4{
+					Port: 1234,
+					Addr: [4]byte{127, 0, 0, 1},
+				},
+			},
+			true,
+			false,
+		},
+		// TODO: Add test cases.
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Ping(tt.args.addr)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Ping() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("Ping() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

lib/sync.go

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+package lib
+
+import (
+	"sync"
+	"time"
+)
+
+type Syncer struct {
+	Delay time.Duration
+	Functions []func()
+}
+
+func (s *Syncer) Start() *sync.WaitGroup {
+	wg := &sync.WaitGroup{}
+	go func() {
+		for _, f := range s.Functions {
+			wg.Add(1)
+			go func(f func()) {
+				f()
+				wg.Done()
+			}(f)
+		}
+		time.Sleep(s.Delay)
+	}()
+	return wg
+}

main.go

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+package main
+
+import (
+	"fmt"
+	"github.com/RyanJarv/little-stitch/lib"
+	"io"
+)
+
+func main() {
+	conn := lib.NewConnection([4]byte{34, 125, 181, 202})
+
+	_, err := io.WriteString(conn, "Hello!")
+	if err != nil {
+		fmt.Printf("failed to write to connection: %s\n", err)
+	}
+}