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channel_test.go
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channel_test.go
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package p9p
import (
"bytes"
"context"
"encoding/binary"
"net"
"testing"
"time"
)
// TestTwriteOverflow ensures that a Twrite message will have the data field
// truncated if the msize would be exceeded.
func TestTwriteOverflow(t *testing.T) {
const (
msize = 512
// size[4] Twrite tag[2] fid[4] offset[8] count[4] data[count] | count = 0
overhead = 4 + 1 + 2 + 4 + 8 + 4
)
var (
ctx = context.Background()
conn = &mockConn{}
ch = NewChannel(conn, msize)
)
for _, testcase := range []struct {
name string
overflow int // amount to overflow the message by.
}{
{
name: "BoundedOverflow",
overflow: msize / 2,
},
{
name: "LargeOverflow",
overflow: msize * 3,
},
{
name: "HeaderOverflow",
overflow: overhead,
},
{
name: "HeaderOffsetOverflow",
overflow: overhead - 1,
},
{
name: "OverflowByOne",
overflow: 1,
},
} {
t.Run(testcase.name, func(t *testing.T) {
var (
fcall = overflowMessage(ch.(*channel).codec, msize, testcase.overflow)
data = fcall.Message.(MessageTwrite).Data
size uint32
)
t.Logf("overflow: %v, len(data): %v, expected overflow: %v", testcase.overflow, len(data), overhead+len(data)-msize)
conn.buf.Reset()
if err := ch.WriteFcall(ctx, fcall); err != nil {
t.Fatal(err)
}
if err := binary.Read(bytes.NewReader(conn.buf.Bytes()), binary.LittleEndian, &size); err != nil {
t.Fatal(err)
}
if size != msize {
t.Fatalf("should have truncated size header: %d != %d", size, msize)
}
if conn.buf.Len() != msize {
t.Fatalf("should have truncated message: conn.buf.Len(%v) != msize(%v)", conn.buf.Len(), msize)
}
})
}
}
// TestWriteOverflowError ensures that we return an error in cases when there
// will certainly be an overflow and it cannot be resolved.
func TestWriteOverflowError(t *testing.T) {
const (
msize = 4
overflowMSize = msize + 1
)
var (
ctx = context.Background()
conn = &mockConn{}
ch = NewChannel(conn, msize)
data = bytes.Repeat([]byte{'A'}, 4)
fcall = newFcall(1, MessageTwrite{
Data: data,
})
messageSize = 4 + ch.(*channel).codec.Size(fcall)
)
err := ch.WriteFcall(ctx, fcall)
if err == nil {
t.Fatal("error expected when overflowing message")
}
if Overflow(err) != messageSize-msize {
t.Fatalf("overflow should reflect messageSize and msize, %d != %d", Overflow(err), messageSize-msize)
}
}
// TestReadOverflow ensures that messages coming over a network connection do
// not overflow the msize. Invalid messages will cause `ReadFcall` to return an
// Overflow error.
func TestReadFcallOverflow(t *testing.T) {
const (
msize = 256
)
var (
ctx = context.Background()
conn = &mockConn{}
ch = NewChannel(conn, msize)
codec = ch.(*channel).codec
)
for _, testcase := range []struct {
name string
overflow int
}{
{
name: "OverflowByOne",
overflow: 1,
},
{
name: "HeaderOverflow",
overflow: overheadMessage(codec, MessageTwrite{}),
},
{
name: "HeaderOffsetOverflow",
overflow: overheadMessage(codec, MessageTwrite{}) - 1,
},
} {
t.Run(testcase.name, func(t *testing.T) {
fcall := overflowMessage(codec, msize, testcase.overflow)
// prepare the raw message
p, err := ch.(*channel).codec.Marshal(fcall)
if err != nil {
t.Fatal(err)
}
// "send" the message into the buffer
// this message is crafted to overflow the read buffer.
if err := sendmsg(&conn.buf, p); err != nil {
t.Fatal(err)
}
var incoming Fcall
err = ch.ReadFcall(ctx, &incoming)
if err == nil {
t.Fatal("expected error on fcall")
}
// sanity check to ensure our test code has the right overflow
if testcase.overflow != ch.(*channel).msgmsize(fcall)-msize {
t.Fatalf("overflow calculation incorrect: %v != %v", testcase.overflow, ch.(*channel).msgmsize(fcall)-msize)
}
if Overflow(err) != testcase.overflow {
t.Fatalf("unexpected overflow on error: %v !=%v", Overflow(err), testcase.overflow)
}
})
}
}
// TestTreadRewrite ensures that messages that whose response would overflow
// the msize will have be adjusted before sending.
func TestTreadRewrite(t *testing.T) {
const (
msize = 256
overflowMSize = msize + 1
)
var (
ctx = context.Background()
conn = &mockConn{}
ch = NewChannel(conn, msize)
buf = make([]byte, overflowMSize)
// data = bytes.Repeat([]byte{'A'}, overflowMSize)
fcall = newFcall(1, MessageTread{
Count: overflowMSize,
})
responseMSize = ch.(*channel).msgmsize(newFcall(1, MessageRread{
Data: buf,
}))
)
if err := ch.WriteFcall(ctx, fcall); err != nil {
t.Fatal(err)
}
// just read the message off the buffer
n, err := readmsg(&conn.buf, buf)
if err != nil {
t.Fatal(err)
}
*fcall = Fcall{}
if err := ch.(*channel).codec.Unmarshal(buf[:n], fcall); err != nil {
t.Fatal(err)
}
tread, ok := fcall.Message.(MessageTread)
if !ok {
t.Fatalf("unexpected message: %v", fcall)
}
if tread.Count != overflowMSize-(uint32(responseMSize)-msize) {
t.Fatalf("count not rewritten: %v != %v", tread.Count, overflowMSize-(uint32(responseMSize)-msize))
}
}
type mockConn struct {
net.Conn
buf bytes.Buffer
}
func (m mockConn) SetWriteDeadline(t time.Time) error { return nil }
func (m mockConn) SetReadDeadline(t time.Time) error { return nil }
func (m *mockConn) Write(p []byte) (int, error) {
return m.buf.Write(p)
}
func (m *mockConn) Read(p []byte) (int, error) {
return m.buf.Read(p)
}
func overheadMessage(codec Codec, msg Message) int {
return 4 + codec.Size(newFcall(1, msg))
}
// overflowMessage returns message that overflows the msize by overflow bytes,
// returning the message size and the fcall.
func overflowMessage(codec Codec, msize, overflow int) *Fcall {
var (
overhead = overheadMessage(codec, MessageTwrite{})
data = bytes.Repeat([]byte{'A'}, (msize-overhead)+overflow)
fcall = newFcall(1, MessageTwrite{
Data: data,
})
)
return fcall
}