Rule is defined as follows in rule.go:

type Rule struct {
  // ...
  Mark              int
  Mask              int
  // ...
}

The default value for Mark and Mask is -1 when creating an instance of Rule with NewRule, and this translates in the corresponding attributes being omitted from the generated netlink message:

	if rule.Mark >= 0 {
		b := make([]byte, 4)
		native.PutUint32(b, uint32(rule.Mark))
		req.AddData(nl.NewRtAttr(nl.FRA_FWMARK, b))
	}
	if rule.Mask >= 0 {
		b := make([]byte, 4)
		native.PutUint32(b, uint32(rule.Mask))
		req.AddData(nl.NewRtAttr(nl.FRA_FWMASK, b))
	}

I have a package that uses github.com/vishvananda/netlink as follows:

ipRule := netlink.NewRule()
ipRule.Mark = 1 << 31
ipRule.Mask = 0xffffffff # same as using the default (-1), but writing this makes sense to be explicit
...

When I try to build this code for a 32-bit architecture (in my case arm/v7), I get errors like this:

constant 2147483648 overflows int
constant 4294967295 overflows int

Would it be possible to change the type of Mark and Mask in order to have better support for 32-bit architectures? I would suggest making these fields *int32 values.

(I have limited knowledge of ip rule but I am assuming that 1 << 31 is a legit fwmark value).