net/http: http.ReadResponse does not handle 100-continue

[geofffranks]

Go version

go 1.22.5, but also on go.dev/play on 1.23

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/pivotal/.cache/go-build'
GOENV='/home/pivotal/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/pivotal/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/pivotal/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.22.5'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3271148184=/tmp/go-build -gno-record-gcc-switches'

What did you do?

Issue two requests with Expect: 100-continue headers, to the same server. One using http.DefaultClient.Do(), and the other using raw network connections and parsing the output. Then examine the returned data.

Reproduction on go.dev

What did you see happen?

The final status code in the response object was 100.

What did you expect to see?

The final status code returned should be a 405 (method not allowed). There may be other differences in how http.ReadResponse() works compared to the readResponse() function in transport.go as well. Can the logic for those two functions be shared?

[ianlancetaylor]

CC @neild @bradfitz

[gabyhelp]

Related Issues and Documentation

• net/http: Several 100-continue #22128 (closed)
• net/http: client `Expect: 100-continue` reads first byte of input on failure #16002 (closed)
• net/http: unexpected 1XX status codes are not handled well #17739 (closed)
• net/http: Client hangs forever on 101 Status Code #44988
• net/http Server provides no way for a Handler to respond to a client with an error before a 100-continue #17664 (closed)
• net/http: RoundTrip hangs for request with Expect: 100-continue if the server skips continue frame #45834
• net/http: client `Expect: 100-continue` docs not clear #16003 (closed)
• net/http: HTTP server should respond with 100 Continue for zero-length "Expect: 100-continue" requests #16799 (closed)
• net/http: ResponseHeaderTimeout not honoured - response from server not visible to implementing part #40926
• net/http: Expect: 100-continue changes behaviour if server closes request body #63152

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