golang/go

net/textproto: swallows errors returned by underlying reader

Open

#53,858 opened on Jul 13, 2022

View on GitHub
 (13 comments) (0 reactions) (0 assignees)Go (19,008 forks)batch import
NeedsFixhelp wanted

Repository metrics

Stars
 (133,883 stars)
PR merge metrics
 (No merged PRs in 30d)

Description

What version of Go are you using (go version)?

Does this issue reproduce with the latest release?

Yes.

What did you do?

See example: https://go.dev/play/p/Bn8H6p4QUf6

What did you expect to see?

I expect that bufio package react on underlying reader errors and stop the reading.

What did you see instead?

I see that bufio skips an error multiple times, and the example code causes OOM error becuase reader is rewinded every time:

here are cases when an error is not tracked: https://cs.opensource.google/go/go/+/refs/tags/go1.18.4:src/net/textproto/reader.go;l=148;drc=27794c4d4a18c61d8c158d253421d72b5a6a8673 https://cs.opensource.google/go/go/+/refs/tags/go1.18.4:src/net/textproto/reader.go;l=496;drc=27794c4d4a18c61d8c158d253421d72b5a6a8673 https://cs.opensource.google/go/go/+/refs/tags/go1.18.4:src/net/textproto/reader.go;l=566;drc=27794c4d4a18c61d8c158d253421d72b5a6a8673 https://cs.opensource.google/go/go/+/refs/tags/go1.18.4:src/net/textproto/reader.go;l=571;drc=27794c4d4a18c61d8c158d253421d72b5a6a8673

the error, returned by autoRewind is just ignored and set to nil: https://cs.opensource.google/go/go/+/refs/tags/go1.18.4:src/bufio/bufio.go;l=156;drc=27794c4d4a18c61d8c158d253421d72b5a6a8673 https://cs.opensource.google/go/go/+/refs/tags/go1.18.4:src/bufio/bufio.go;l=124;drc=27794c4d4a18c61d8c158d253421d72b5a6a8673

I know that it's something that I have to expect with autoRewind, but this behavior caused an unpleasant surprise.

see also:

Contributor guide

Research direction
Investigate how bufio.Reader discards errors during autoRewind and how net/textproto.ReadMIMEHeader ignores those errors. Trace the code paths in bufio.go and reader.go linked in the issue.
Tech stack
go
Domain
api
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Gobufio
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60