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util/deephash: disambiguate hashing of AppendTo (#2483) 

Prepend size to AppendTo output.

Fixes #2443

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai 2021-07-21 11:29:08 -07:00 committed by GitHub
parent 23ad028414
commit d666bd8533
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 12 additions and 2 deletions
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6
util/deephash/deephash.go
View File

@ -147,8 +147,10 @@ func (h *hasher) print(v reflect.Value) (acyclic bool) {
// Use AppendTo methods, if available and cheap.
if v.CanAddr() && v.Type().Implements(appenderToType) {
a := v.Addr().Interface().(appenderTo)
scratch := a.AppendTo(h.scratch[:0])
w.Write(scratch)
size := h.scratch[:8]
record := a.AppendTo(size)
binary.LittleEndian.PutUint64(record, uint64(len(record)-len(size)))
w.Write(record)
return true
}
}

8
util/deephash/deephash_test.go
View File

@ -22,6 +22,12 @@ import (
"tailscale.com/wgengine/wgcfg"
)
type appendBytes []byte
func (p appendBytes) AppendTo(b []byte) []byte {
return append(b, p...)
}
func TestHash(t *testing.T) {
type tuple [2]interface{}
type iface struct{ X interface{} }
@ -31,6 +37,8 @@ func TestHash(t *testing.T) {
in tuple
wantEq bool
}{
{in: tuple{[]appendBytes{{}, {0, 0, 0, 0, 0, 0, 0, 1}}, []appendBytes{{}, {0, 0, 0, 0, 0, 0, 0, 1}}}, wantEq: true},
{in: tuple{[]appendBytes{{}, {0, 0, 0, 0, 0, 0, 0, 1}}, []appendBytes{{0, 0, 0, 0, 0, 0, 0, 1}, {}}}, wantEq: false},
{in: tuple{iface{MyBool(true)}, iface{MyBool(true)}}, wantEq: true},
{in: tuple{iface{true}, iface{MyBool(true)}}, wantEq: false},
{in: tuple{iface{MyHeader{}}, iface{MyHeader{}}}, wantEq: true},