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Disable lineLimitReader when handle BDAT data #139

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merged 7 commits into from
Mar 24, 2021
+16 −9
Merged

Disable lineLimitReader when handle BDAT data #139

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0cbd1b1
Fix bDatHandle. Remove use limitReader on handle read binaryMime bytes
Mar 22, 2021
3c72164
Disable lineLimitReader when use handle BDAT data
Mar 22, 2021
a5f341b
Rework lenghtlimit_reader
Mar 22, 2021
833db20
Correct defer for handleBdat
Mar 23, 2021
ecc2877
Fix name of defer function
Mar 23, 2021
4569335
Fix recover LineLimit
Mar 24, 2021
e998800
Add recover lineLimit on copy error
Mar 24, 2021
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23 changes: 15 additions & 8 deletions conn.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,10 +40,11 @@ type Conn struct {
locker sync.Mutex
binarymime bool

bdatPipe *io.PipeWriter
bdatStatus *statusCollector // used for BDAT on LMTP
dataResult chan error
bytesReceived int // counts total size of chunks when BDAT is used
lineLimitReader *lineLimitReader
bdatPipe *io.PipeWriter
bdatStatus *statusCollector // used for BDAT on LMTP
dataResult chan error
bytesReceived int // counts total size of chunks when BDAT is used

fromReceived bool
recipients []string
Expand All @@ -60,15 +61,16 @@ func newConn(c net.Conn, s *Server) *Conn {
}

func (c *Conn) init() {
c.lineLimitReader = &lineLimitReader{
R: c.conn,
LineLimit: c.server.MaxLineLength,
}
rwc := struct {
io.Reader
io.Writer
io.Closer
}{
Reader: &lineLimitReader{
R: c.conn,
LineLimit: c.server.MaxLineLength,
},
Reader: c.lineLimitReader,
Writer: c.conn,
Closer: c.conn,
}
Expand Down Expand Up @@ -739,6 +741,8 @@ func (c *Conn) handleBdat(arg string) {
}()
}

prevLineLimit := c.lineLimitReader.LineLimit
c.lineLimitReader.LineLimit = 0
chunk := io.LimitReader(c.text.R, int64(size))
_, err = io.Copy(c.bdatPipe, chunk)
if err != nil {
Expand All @@ -753,6 +757,7 @@ func (c *Conn) handleBdat(arg string) {
}

c.reset()
c.lineLimitReader.LineLimit = prevLineLimit
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@emersion emersion Mar 22, 2021 •
edited
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Instead of duplicating these statements, can we maybe use defer here?

prevLineLimit := c.lineLimitReader.LineLimit
c.lineLimitReader.LineLimit = 0
defer func() {
	c.lineLimitReader.LineLimit = prevLineLimit
}()

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I try it. But it not worked as expected.

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Hm, what went wrong exactly?

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It just don't work. If i'm add defer and first chunk handle return error TooLongLine.

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Hm, what went wrong exactly?

I found problem. This code

defer func() {
	c.lineLimitReader.LineLimit = prevLineLimit
}()

Run go routine and this can run defer and next handle at same time. I fix that with this code

	recover := func() {
		c.lineLimitReader.LineLimit = prevLineLimit
	}
	defer recover()

this fix problem same time running defer goroutine and next handleBdat

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I don't really understand why it doesn't work without the intermediary variable. It definitely should.

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It worked. But defer run in goroutine. This goroutine code

func() {
	c.lineLimitReader.LineLimit = prevLineLimit
}()

And some time next handleBdat running before running defer. After this when we try copy chunk

 io.Copy(c.bdatPipe, chunk)

Read return ErrTooLongLine

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defer doesn't run in a separate goroutine...

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Okey i'm research problem deeper and create new fix. First we should't restore limit before got BDAT LAST command. It's broke In some cases and return error ToooLongTime. For example read next BDAT command. I'm just put restore lineLimit in last condition and this fix problem.

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Oh you're right, if the BDAT transfer is still ongoing, we shouldn't restore the limit.

return
}

Expand All @@ -775,13 +780,15 @@ func (c *Conn) handleBdat(arg string) {

if err == errPanic {
c.Close()
c.lineLimitReader.LineLimit = prevLineLimit
return
}

c.reset()
} else {
c.WriteResponse(250, EnhancedCode{2, 0, 0}, "Continue")
}
c.lineLimitReader.LineLimit = prevLineLimit
}

// ErrDataReset is returned by Reader pased to Data function if client does not
Expand Down
2 changes: 1 addition & 1 deletion lengthlimit_reader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ type lineLimitReader struct {
}

func (r *lineLimitReader) Read(b []byte) (int, error) {
if r.curLineLength > r.LineLimit {
if r.curLineLength > r.LineLimit && r.LineLimit > 0 {
return 0, ErrTooLongLine
}

Expand Down