Remove three syserror entries duplicated in linuxerr. Because of the
linuxerr.Equals method, this is a mere change of return values from
syserror to linuxerr definitions.
Done with only these three errnos as CLs removing all grow to a significantly
large size.
PiperOrigin-RevId: 382173835
Before fix, use of this flag causes an error.
It affects applications like OpenVPN which sets this flag for legacy reasons.
According to linux/if_tun.h "This flag has no real effect".
Doing so involved breaking dependencies between //pkg/tcpip and the rest
of gVisor, which are discouraged anyways.
Tested on the Go branch via:
gvisor.dev/gvisor/pkg/tcpip/...
Addresses #1446.
PiperOrigin-RevId: 363081778
