Rework some things into packages (#489)

udp/udp_linux_32.go

@@ -0,0 +1,55 @@
+//go:build linux && (386 || amd64p32 || arm || mips || mipsle) && !android && !e2e_testing
+// +build linux
+// +build 386 amd64p32 arm mips mipsle
+// +build !android
+// +build !e2e_testing
+
+package udp
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+type iovec struct {
+	Base *byte
+	Len  uint32
+}
+
+type msghdr struct {
+	Name       *byte
+	Namelen    uint32
+	Iov        *iovec
+	Iovlen     uint32
+	Control    *byte
+	Controllen uint32
+	Flags      int32
+}
+
+type rawMessage struct {
+	Hdr msghdr
+	Len uint32
+}
+
+func (u *Conn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
+	msgs := make([]rawMessage, n)
+	buffers := make([][]byte, n)
+	names := make([][]byte, n)
+
+	for i := range msgs {
+		buffers[i] = make([]byte, MTU)
+		names[i] = make([]byte, unix.SizeofSockaddrInet6)
+
+		//TODO: this is still silly, no need for an array
+		vs := []iovec{
+			{Base: &buffers[i][0], Len: uint32(len(buffers[i]))},
+		}
+
+		msgs[i].Hdr.Iov = &vs[0]
+		msgs[i].Hdr.Iovlen = uint32(len(vs))
+
+		msgs[i].Hdr.Name = &names[i][0]
+		msgs[i].Hdr.Namelen = uint32(len(names[i]))
+	}
+
+	return msgs, buffers, names
+}