1 files changed, 159 insertions, 0 deletions
diff --git a/conn/control_linux.go b/conn/control_linux.go
new file mode 100644
index 0000000..44a94e6
--- /dev/null
+++ b/conn/control_linux.go
@@ -0,0 +1,159 @@
+//go:build linux && !android
+
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ */
+
+package conn
+
+import (
+	"fmt"
+	"net/netip"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+func (e *StdNetEndpoint) SrcIP() netip.Addr {
+	switch len(e.src) {
+	case unix.CmsgSpace(unix.SizeofInet4Pktinfo):
+		info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
+		return netip.AddrFrom4(info.Spec_dst)
+	case unix.CmsgSpace(unix.SizeofInet6Pktinfo):
+		info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
+		// TODO: set zone. in order to do so we need to check if the address is
+		// link local, and if it is perform a syscall to turn the ifindex into a
+		// zone string because netip uses string zones.
+		return netip.AddrFrom16(info.Addr)
+	}
+	return netip.Addr{}
+}
+
+func (e *StdNetEndpoint) SrcIfidx() int32 {
+	switch len(e.src) {
+	case unix.CmsgSpace(unix.SizeofInet4Pktinfo):
+		info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
+		return info.Ifindex
+	case unix.CmsgSpace(unix.SizeofInet6Pktinfo):
+		info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
+		return int32(info.Ifindex)
+	}
+	return 0
+}
+
+func (e *StdNetEndpoint) SrcToString() string {
+	return e.SrcIP().String()
+}
+
+// getSrcFromControl parses the control for PKTINFO and if found updates ep with
+// the source information found.
+func getSrcFromControl(control []byte, ep *StdNetEndpoint) {
+	ep.ClearSrc()
+
+	var (
+		hdr  unix.Cmsghdr
+		data []byte
+		rem  []byte = control
+		err  error
+	)
+
+	for len(rem) > unix.SizeofCmsghdr {
+		hdr, data, rem, err = unix.ParseOneSocketControlMessage(rem)
+		if err != nil {
+			return
+		}
+
+		if hdr.Level == unix.IPPROTO_IP &&
+			hdr.Type == unix.IP_PKTINFO {
+
+			if ep.src == nil || cap(ep.src) < unix.CmsgSpace(unix.SizeofInet4Pktinfo) {
+				ep.src = make([]byte, 0, unix.CmsgSpace(unix.SizeofInet4Pktinfo))
+			}
+			ep.src = ep.src[:unix.CmsgSpace(unix.SizeofInet4Pktinfo)]
+
+			hdrBuf := unsafe.Slice((*byte)(unsafe.Pointer(&hdr)), unix.SizeofCmsghdr)
+			copy(ep.src, hdrBuf)
+			copy(ep.src[unix.CmsgLen(0):], data)
+			return
+		}
+
+		if hdr.Level == unix.IPPROTO_IPV6 &&
+			hdr.Type == unix.IPV6_PKTINFO {
+
+			if ep.src == nil || cap(ep.src) < unix.CmsgSpace(unix.SizeofInet6Pktinfo) {
+				ep.src = make([]byte, 0, unix.CmsgSpace(unix.SizeofInet6Pktinfo))
+			}
+
+			ep.src = ep.src[:unix.CmsgSpace(unix.SizeofInet6Pktinfo)]
+
+			hdrBuf := unsafe.Slice((*byte)(unsafe.Pointer(&hdr)), unix.SizeofCmsghdr)
+			copy(ep.src, hdrBuf)
+			copy(ep.src[unix.CmsgLen(0):], data)
+			return
+		}
+	}
+}
+
+// setSrcControl sets an IP{V6}_PKTINFO in control based on the source address
+// and source ifindex found in ep. control's len will be set to 0 in the event
+// that ep is a default value.
+func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
+	if cap(*control) < len(ep.src) {
+		return
+	}
+	*control = (*control)[:0]
+	*control = append(*control, ep.src...)
+}
+
+const (
+	sizeOfGSOData = 2
+)
+
+// getGSOSize parses control for UDP_GRO and if found returns its GSO size data.
+func getGSOSize(control []byte) (int, error) {
+	var (
+		hdr  unix.Cmsghdr
+		data []byte
+		rem  = control
+		err  error
+	)
+
+	for len(rem) > unix.SizeofCmsghdr {
+		hdr, data, rem, err = unix.ParseOneSocketControlMessage(rem)
+		if err != nil {
+			return 0, fmt.Errorf("error parsing socket control message: %w", err)
+		}
+		if hdr.Level == unix.SOL_UDP && hdr.Type == unix.UDP_GRO && len(data) >= sizeOfGSOData {
+			var gso uint16
+			copy(unsafe.Slice((*byte)(unsafe.Pointer(&gso)), sizeOfGSOData), data[:sizeOfGSOData])
+			return int(gso), nil
+		}
+	}
+	return 0, nil
+}
+
+// setGSOSize sets a UDP_SEGMENT in control based on gsoSize. It leaves existing
+// data in control untouched.
+func setGSOSize(control *[]byte, gsoSize uint16) {
+	existingLen := len(*control)
+	avail := cap(*control) - existingLen
+	space := unix.CmsgSpace(sizeOfGSOData)
+	if avail < space {
+		return
+	}
+	*control = (*control)[:cap(*control)]
+	gsoControl := (*control)[existingLen:]
+	hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(gsoControl)[0]))
+	hdr.Level = unix.SOL_UDP
+	hdr.Type = unix.UDP_SEGMENT
+	hdr.SetLen(unix.CmsgLen(sizeOfGSOData))
+	copy((gsoControl)[unix.SizeofCmsghdr:], unsafe.Slice((*byte)(unsafe.Pointer(&gsoSize)), sizeOfGSOData))
+	*control = (*control)[:existingLen+space]
+}
+
+// controlSize returns the recommended buffer size for pooling sticky and UDP
+// offloading control data.
+var controlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo) + unix.CmsgSpace(sizeOfGSOData)
+
+const StdNetSupportsStickySockets = true