[netstack] Move SO_PASSCRED option to SocketOptions.

This change also makes the following fixes:
- Make SocketOptions use atomic operations instead of having to acquire/drop
  locks upon each get/set option.
- Make documentation more consistent.
- Remove tcpip.SocketOptions from socketOpsCommon because it already exists
  in transport.Endpoint.
- Refactors get/set socket options tests to be easily extendable.

PiperOrigin-RevId: 343103780

1 files changed, 1 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 440cb0352..fe6514bcd 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -857,6 +857,7 @@ func (*endpoint) LastError() *tcpip.Error {
 	return nil
 }
 
+// SocketOptions implements tcpip.Endpoint.SocketOptions.
 func (e *endpoint) SocketOptions() *tcpip.SocketOptions {
 	return &e.ops
 }