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unix: add ParseOneSocketControlMessage to parse control messages without allocating

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Fixes golang/go#54714.

Change-Id: If711272937078b6c696756823aa4dfcec358b719
Reviewed-on: https://go-review.googlesource.com/c/sys/+/425917
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Matt Layher <mdlayher@gmail.com>
This commit is contained in:
Marten Seemann
2022-08-28 20:57:28 +03:00
committed by Gopher Robot
parent 5726498127
commit fc697a31fa
2 changed files with 32 additions and 1 deletions
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14
unix/sockcmsg_unix.go
View File

@@ -52,6 +52,20 @@ func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) {
return msgs, nil
}
// ParseOneSocketControlMessage parses a single socket control message from b, returning the message header,
// message data (a slice of b), and the remainder of b after that single message.
// When there are no remaining messages, len(remainder) == 0.
func ParseOneSocketControlMessage(b []byte) (hdr Cmsghdr, data []byte, remainder []byte, err error) {
h, dbuf, err := socketControlMessageHeaderAndData(b)
if err != nil {
return Cmsghdr{}, nil, nil, err
}
if i := cmsgAlignOf(int(h.Len)); i < len(b) {
remainder = b[i:]
}
return *h, dbuf, remainder, nil
}
func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) {
h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) {

19
unix/syscall_unix_test.go
View File

@@ -322,7 +322,7 @@ func passFDChild() {
}
}
// TestUnixRightsRoundtrip tests that UnixRights, ParseSocketControlMessage,
// TestUnixRightsRoundtrip tests that UnixRights, ParseSocketControlMessage, ParseOneSocketControlMessage,
// and ParseUnixRights are able to successfully round-trip lists of file descriptors.
func TestUnixRightsRoundtrip(t *testing.T) {
testCases := [...][][]int{
@@ -350,6 +350,23 @@ func TestUnixRightsRoundtrip(t *testing.T) {
if len(scms) != len(testCase) {
t.Fatalf("expected %v SocketControlMessage; got scms = %#v", len(testCase), scms)
}
var c int
for len(b) > 0 {
hdr, data, remainder, err := unix.ParseOneSocketControlMessage(b)
if err != nil {
t.Fatalf("ParseOneSocketControlMessage: %v", err)
}
if scms[c].Header != hdr || !bytes.Equal(scms[c].Data, data) {
t.Fatal("expected SocketControlMessage header and data to match")
}
b = remainder
c++
}
if c != len(scms) {
t.Fatalf("expected %d SocketControlMessages; got %d", len(scms), c)
}
for i, scm := range scms {
gotFds, err := unix.ParseUnixRights(&scm)
if err != nil {