x/net/http2: hpack.(*Encoder).WriteField panic errors

[v-byte-cpu]

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

$ go version
go version go1.16.7 linux/amd64

Does this issue reproduce with the latest release?

Not tested

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/user/.cache/go-build"
GOENV="/home/user/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/user/workspace/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/user/workspace/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.7"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/user/workspace/example/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3609040575=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Making concurrent HTTP/2 requests to server using DefaultClient net/http.(*Client).Do method,
I periodically get the following panic error messages.

panic(0x7fd500, 0xc0000ff730)
        /usr/lib/go/src/runtime/panic.go:965 +0x1b9
vendor/golang.org/x/net/http2/hpack.(*headerFieldTable).idToIndex(0xc0003ee080, 0x20, 0xc00029c6b8)
        /usr/lib/go/src/vendor/golang.org/x/net/http2/hpack/tables.go:119 +0x12c
vendor/golang.org/x/net/http2/hpack.(*headerFieldTable).search(0xc0003ee080, 0xc000405f60, 0xe, 0xc000410280, 0x5, 0x0, 0x0, 0x0)
        /usr/lib/go/src/vendor/golang.org/x/net/http2/hpack/tables.go:106 +0x150
vendor/golang.org/x/net/http2/hpack.(*Encoder).searchTable(0xc0003ee080, 0xc000405f60, 0xe, 0xc000410280, 0x5, 0x0, 0x0, 0x0)
        /usr/lib/go/src/vendor/golang.org/x/net/http2/hpack/encode.go:97 +0x92
vendor/golang.org/x/net/http2/hpack.(*Encoder).WriteField(0xc0003ee080, 0xc000405f60, 0xe, 0xc000410280, 0x5, 0x0, 0x0, 0x0)
        /usr/lib/go/src/vendor/golang.org/x/net/http2/hpack/encode.go:62 +0x20a
net/http.(*http2ClientConn).writeHeader(0xc000294d80, 0xc000405f60, 0xe, 0xc000410280, 0x5)
        /usr/lib/go/src/net/http/h2_bundle.go:8183 +0xbc
net/http.(*http2ClientConn).encodeHeaders.func3(0xc000405780, 0xe, 0xc000410280, 0x5)
        /usr/lib/go/src/net/http/h2_bundle.go:8122 +0x93
net/http.(*http2ClientConn).encodeHeaders.func1(0xc00029cb50)
        /usr/lib/go/src/net/http/h2_bundle.go:8088 +0x3d5
net/http.(*http2ClientConn).encodeHeaders(0xc000294d80, 0xc000c28800, 0x1, 0x0, 0x0, 0xffffffffffffffff, 0x881553, 0x10000000000000e, 0x7effe9ae8550, 0x0, ...)
        /usr/lib/go/src/net/http/h2_bundle.go:8120 +0x5e8
net/http.(*http2ClientConn).roundTrip(0xc000294d80, 0xc000c28800, 0x0, 0x0, 0x0, 0x0)
        /usr/lib/go/src/net/http/h2_bundle.go:7583 +0x2bb
net/http.(*http2Transport).RoundTripOpt(0xc0002ae700, 0xc000c28800, 0x810e00, 0xc000288480, 0x87e638, 0x5)
        /usr/lib/go/src/net/http/h2_bundle.go:6981 +0x1a5
net/http.(*http2Transport).RoundTrip(...)
        /usr/lib/go/src/net/http/h2_bundle.go:6942
net/http.http2noDialH2RoundTripper.RoundTrip(0xc0002ae700, 0xc000c28800, 0x9020a0, 0xc0002ae700, 0x0)
        /usr/lib/go/src/net/http/h2_bundle.go:9197 +0x3e
net/http.(*Transport).roundTrip(0xb87a00, 0xc000c28700, 0x7f0013b98f18, 0x580, 0xc000c5f700)
        /usr/lib/go/src/net/http/transport.go:537 +0xdec
net/http.(*Transport).RoundTrip(0xb87a00, 0xc000c28700, 0xb87a00, 0x0, 0x0)
        /usr/lib/go/src/net/http/roundtrip.go:17 +0x35
net/http.send(0xc000c28700, 0x901640, 0xb87a00, 0x0, 0x0, 0x0, 0xc000aceb18, 0xc000a44a80, 0x1, 0x0)
        /usr/lib/go/src/net/http/client.go:251 +0x454
net/http.(*Client).send(0xc0001b8660, 0xc000c28700, 0x0, 0x0, 0x0, 0xc000aceb18, 0x0, 0x1, 0x2a)
        /usr/lib/go/src/net/http/client.go:175 +0xff
net/http.(*Client).do(0xc0001b8660, 0xc000c28700, 0x0, 0x0, 0x0)
        /usr/lib/go/src/net/http/client.go:717 +0x45f
net/http.(*Client).Do(0xc0001b8660, 0xc000c28700, 0xc000c28700, 0x0, 0x0)
        /usr/lib/go/src/net/http/client.go:585 +0x35

What did you expect to see?

No panic errors

What did you see instead?

Panic errors

[seankhliao]

have you tried running it under the race detector?

[v-byte-cpu]

yes, sure, I built an app using go build -race and started again, a panic error occurred, but a data race report was not generated.

[AlexanderYastrebov]

Apparently duplicate of #43051

[neild]

Duplicate of #43051.

(Added a comment there--tl;dr, if you ever write requests with trailers, this may have been fixed already in x/net.)