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dns/dnsmessage: compress all names while appending to a buffer

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Change-Id: Iedccbf3e47a63b2239def189ab41bab18a64c398
GitHub-Last-Rev: eb23195734
GitHub-Pull-Request: golang/net#189
Reviewed-on: https://go-review.googlesource.com/c/net/+/522575
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Mateusz Poliwczak <mpoliwczak34@gmail.com>
Reviewed-by: Joedian Reid <joedian@golang.org>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Mateusz Poliwczak
2023-08-28 16:40:48 +00:00
committed by Gopher Robot
parent 8b010a5243
commit b4d09be751
2 changed files with 31 additions and 3 deletions
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7
dns/dnsmessage/message.go
View File

@@ -2000,14 +2000,15 @@ func (n *Name) pack(msg []byte, compression map[string]int, compressionOff int)
}
// Miss. Add the suffix to the compression table if the
// offset can be stored in the available 14 bytes.
if len(msg) <= int(^uint16(0)>>2) {
// offset can be stored in the available 14 bits.
newPtr := len(msg) - compressionOff
if newPtr <= int(^uint16(0)>>2) {
if nameAsStr == "" {
// allocate n.Data on the heap once, to avoid allocating it
// multiple times (for next labels).
nameAsStr = string(n.Data[:n.Length])
}
compression[nameAsStr[i:]] = len(msg) - compressionOff
compression[nameAsStr[i:]] = newPtr
}
}
}

27
dns/dnsmessage/message_test.go
View File

@@ -1847,3 +1847,30 @@ func TestBuilderNameCompressionWithNonZeroedName(t *testing.T) {
t.Fatalf("b.Finish() = %v, want: %v", msg, expect)
}
}
func TestBuilderCompressionInAppendMode(t *testing.T) {
maxPtr := int(^uint16(0) >> 2)
b := NewBuilder(make([]byte, maxPtr, maxPtr+512), Header{})
b.EnableCompression()
if err := b.StartQuestions(); err != nil {
t.Fatalf("b.StartQuestions() unexpected error: %v", err)
}
if err := b.Question(Question{Name: MustNewName("go.dev.")}); err != nil {
t.Fatalf("b.Question() unexpected error: %v", err)
}
if err := b.Question(Question{Name: MustNewName("go.dev.")}); err != nil {
t.Fatalf("b.Question() unexpected error: %v", err)
}
msg, err := b.Finish()
if err != nil {
t.Fatalf("b.Finish() unexpected error: %v", err)
}
expect := []byte{
0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, // header
2, 'g', 'o', 3, 'd', 'e', 'v', 0, 0, 0, 0, 0, // question 1
0xC0, 12, 0, 0, 0, 0, // question 2
}
if !bytes.Equal(msg[maxPtr:], expect) {
t.Fatalf("msg[maxPtr:] = %v, want: %v", msg[maxPtr:], expect)
}
}