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Annotate Execute() errors using netlink error message.

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This patch makes two changes:
- setsockopt NETLINK_EXT_ACK, if EnableErrorMessageReporting is
  configured. (defaults to false for compatibility with existing code)
- NetlinkRequest.Execute is modified to parse the nlmsgerr attributes
  if they are present on the response message.
  - After this patch, when the request results in NLMSG_ERROR and the
    response contains a netlink error message (NLMSGERR_ATTR_MSG),
    NetlinkRequest.Execute will return an error with the message that
    wraps syscall.Errno.
This commit is contained in:
yzp0n 2022-01-30 16:21:01 +09:00 committed by Vish (Ishaya) Abrams
parent f7fd7af437
commit facc790515
1 changed files with 59 additions and 3 deletions
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62
nl/nl_linux.go
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@ -39,6 +39,9 @@ var nextSeqNr uint32
// Default netlink socket timeout, 60s
var SocketTimeoutTv = unix.Timeval{Sec: 60, Usec: 0}
// ErrorMessageReporting is the default error message reporting configuration for the new netlink sockets
var EnableErrorMessageReporting bool = false
// GetIPFamily returns the family type of a net.IP.
func GetIPFamily(ip net.IP) int {
if len(ip) <= net.IPv4len {
@ -81,6 +84,14 @@ func Swap32(i uint32) uint32 {
return (i&0xff000000)>>24 | (i&0xff0000)>>8 | (i&0xff00)<<8 | (i&0xff)<<24
}
const (
NLMSGERR_ATTR_UNUSED = 0
NLMSGERR_ATTR_MSG = 1
NLMSGERR_ATTR_OFFS = 2
NLMSGERR_ATTR_COOKIE = 3
NLMSGERR_ATTR_POLICY = 4
)
type NetlinkRequestData interface {
Len() int
Serialize() []byte
@ -303,6 +314,12 @@ func (msg *IfInfomsg) EncapType() string {
return fmt.Sprintf("unknown%d", msg.Type)
}
// Round the length of a netlink message up to align it properly.
// Taken from syscall/netlink_linux.go by The Go Authors under BSD-style license.
func nlmAlignOf(msglen int) int {
return (msglen + syscall.NLMSG_ALIGNTO - 1) & ^(syscall.NLMSG_ALIGNTO - 1)
}
func rtaAlignOf(attrlen int) int {
return (attrlen + unix.RTA_ALIGNTO - 1) & ^(unix.RTA_ALIGNTO - 1)
}
@ -487,6 +504,9 @@ func (req *NetlinkRequest) Execute(sockType int, resType uint16) ([][]byte, erro
if err := s.SetReceiveTimeout(&SocketTimeoutTv); err != nil {
return nil, err
}
if err := s.SetExtAck(EnableErrorMessageReporting); err != nil {
return nil, err
}
defer s.Close()
} else {
@ -526,11 +546,37 @@ done:
}
if m.Header.Type == unix.NLMSG_DONE || m.Header.Type == unix.NLMSG_ERROR {
native := NativeEndian()
error := int32(native.Uint32(m.Data[0:4]))
if error == 0 {
errno := int32(native.Uint32(m.Data[0:4]))
if errno == 0 {
break done
}
return nil, syscall.Errno(-error)
var err error
err = syscall.Errno(-errno)
unreadData := m.Data[4:]
if m.Header.Flags|unix.NLM_F_ACK_TLVS != 0 && len(unreadData) > syscall.SizeofNlMsghdr {
// Skip the echoed request message.
echoReqH := (*syscall.NlMsghdr)(unsafe.Pointer(&unreadData[0]))
unreadData = unreadData[nlmAlignOf(int(echoReqH.Len)):]
// Annotate `err` using nlmsgerr attributes.
for len(unreadData) >= syscall.SizeofRtAttr {
attr := (*syscall.RtAttr)(unsafe.Pointer(&unreadData[0]))
attrData := unreadData[syscall.SizeofRtAttr:attr.Len]
switch attr.Type {
case NLMSGERR_ATTR_MSG:
err = fmt.Errorf("%w: %s", err, string(attrData))
default:
// TODO: handle other NLMSGERR_ATTR types
}
unreadData = unreadData[rtaAlignOf(int(attr.Len)):]
}
}
return nil, err
}
if resType != 0 && m.Header.Type != resType {
continue
@ -745,6 +791,16 @@ func (s *NetlinkSocket) SetReceiveTimeout(timeout *unix.Timeval) error {
return unix.SetsockoptTimeval(int(s.fd), unix.SOL_SOCKET, unix.SO_RCVTIMEO, timeout)
}
// SetExtAck requests error messages to be reported on the socket
func (s *NetlinkSocket) SetExtAck(enable bool) error {
var enableN int
if enable {
enableN = 1
}
return unix.SetsockoptInt(int(s.fd), unix.SOL_NETLINK, unix.NETLINK_EXT_ACK, enableN)
}
func (s *NetlinkSocket) GetPid() (uint32, error) {
fd := int(atomic.LoadInt32(&s.fd))
lsa, err := unix.Getsockname(fd)