1 files changed, 246 insertions, 0 deletions
diff --git a/pkg/sentry/socket/hostinet/stack.go b/pkg/sentry/socket/hostinet/stack.go
new file mode 100644
index 000000000..9c45991ba
--- /dev/null
+++ b/pkg/sentry/socket/hostinet/stack.go
@@ -0,0 +1,246 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hostinet
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/binary"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/inet"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+var defaultRecvBufSize = inet.TCPBufferSize{
+	Min:     4096,
+	Default: 87380,
+	Max:     6291456,
+}
+
+var defaultSendBufSize = inet.TCPBufferSize{
+	Min:     4096,
+	Default: 16384,
+	Max:     4194304,
+}
+
+// Stack implements inet.Stack for host sockets.
+type Stack struct {
+	// Stack is immutable.
+	interfaces     map[int32]inet.Interface
+	interfaceAddrs map[int32][]inet.InterfaceAddr
+	supportsIPv6   bool
+	tcpRecvBufSize inet.TCPBufferSize
+	tcpSendBufSize inet.TCPBufferSize
+	tcpSACKEnabled bool
+}
+
+// NewStack returns an empty Stack containing no configuration.
+func NewStack() *Stack {
+	return &Stack{
+		interfaces:     make(map[int32]inet.Interface),
+		interfaceAddrs: make(map[int32][]inet.InterfaceAddr),
+	}
+}
+
+// Configure sets up the stack using the current state of the host network.
+func (s *Stack) Configure() error {
+	if err := addHostInterfaces(s); err != nil {
+		return err
+	}
+
+	if _, err := os.Stat("/proc/net/if_inet6"); err == nil {
+		s.supportsIPv6 = true
+	}
+
+	s.tcpRecvBufSize = defaultRecvBufSize
+	if tcpRMem, err := readTCPBufferSizeFile("/proc/sys/net/ipv4/tcp_rmem"); err == nil {
+		s.tcpRecvBufSize = tcpRMem
+	} else {
+		log.Warningf("Failed to read TCP receive buffer size, using default values")
+	}
+
+	s.tcpSendBufSize = defaultSendBufSize
+	if tcpWMem, err := readTCPBufferSizeFile("/proc/sys/net/ipv4/tcp_wmem"); err == nil {
+		s.tcpSendBufSize = tcpWMem
+	} else {
+		log.Warningf("Failed to read TCP send buffer size, using default values")
+	}
+
+	// SACK is important for performance and even compatibility, assume it's
+	// enabled if we can't find the actual value.
+	s.tcpSACKEnabled = true
+	if sack, err := ioutil.ReadFile("/proc/sys/net/ipv4/tcp_sack"); err == nil {
+		s.tcpSACKEnabled = strings.TrimSpace(string(sack)) != "0"
+	} else {
+		log.Warningf("Failed to read if TCP SACK if enabled, setting to true")
+	}
+
+	return nil
+}
+
+// ExtractHostInterfaces will populate an interface map and
+// interfaceAddrs map with the results of the equivalent
+// netlink messages.
+func ExtractHostInterfaces(links []syscall.NetlinkMessage, addrs []syscall.NetlinkMessage, interfaces map[int32]inet.Interface, interfaceAddrs map[int32][]inet.InterfaceAddr) error {
+	for _, link := range links {
+		if link.Header.Type != syscall.RTM_NEWLINK {
+			continue
+		}
+		if len(link.Data) < syscall.SizeofIfInfomsg {
+			return fmt.Errorf("RTM_GETLINK returned RTM_NEWLINK message with invalid data length (%d bytes, expected at least %d bytes)", len(link.Data), syscall.SizeofIfInfomsg)
+		}
+		var ifinfo syscall.IfInfomsg
+		binary.Unmarshal(link.Data[:syscall.SizeofIfInfomsg], usermem.ByteOrder, &ifinfo)
+		inetIF := inet.Interface{
+			DeviceType: ifinfo.Type,
+			Flags:      ifinfo.Flags,
+		}
+		// Not clearly documented: syscall.ParseNetlinkRouteAttr will check the
+		// syscall.NetlinkMessage.Header.Type and skip the struct ifinfomsg
+		// accordingly.
+		attrs, err := syscall.ParseNetlinkRouteAttr(&link)
+		if err != nil {
+			return fmt.Errorf("RTM_GETLINK returned RTM_NEWLINK message with invalid rtattrs: %v", err)
+		}
+		for _, attr := range attrs {
+			switch attr.Attr.Type {
+			case syscall.IFLA_ADDRESS:
+				inetIF.Addr = attr.Value
+			case syscall.IFLA_IFNAME:
+				inetIF.Name = string(attr.Value[:len(attr.Value)-1])
+			}
+		}
+		interfaces[ifinfo.Index] = inetIF
+	}
+
+	for _, addr := range addrs {
+		if addr.Header.Type != syscall.RTM_NEWADDR {
+			continue
+		}
+		if len(addr.Data) < syscall.SizeofIfAddrmsg {
+			return fmt.Errorf("RTM_GETADDR returned RTM_NEWADDR message with invalid data length (%d bytes, expected at least %d bytes)", len(addr.Data), syscall.SizeofIfAddrmsg)
+		}
+		var ifaddr syscall.IfAddrmsg
+		binary.Unmarshal(addr.Data[:syscall.SizeofIfAddrmsg], usermem.ByteOrder, &ifaddr)
+		inetAddr := inet.InterfaceAddr{
+			Family:    ifaddr.Family,
+			PrefixLen: ifaddr.Prefixlen,
+			Flags:     ifaddr.Flags,
+		}
+		attrs, err := syscall.ParseNetlinkRouteAttr(&addr)
+		if err != nil {
+			return fmt.Errorf("RTM_GETADDR returned RTM_NEWADDR message with invalid rtattrs: %v", err)
+		}
+		for _, attr := range attrs {
+			switch attr.Attr.Type {
+			case syscall.IFA_ADDRESS:
+				inetAddr.Addr = attr.Value
+			}
+		}
+		interfaceAddrs[int32(ifaddr.Index)] = append(interfaceAddrs[int32(ifaddr.Index)], inetAddr)
+	}
+
+	return nil
+}
+
+func addHostInterfaces(s *Stack) error {
+	links, err := doNetlinkRouteRequest(syscall.RTM_GETLINK)
+	if err != nil {
+		return fmt.Errorf("RTM_GETLINK failed: %v", err)
+	}
+
+	addrs, err := doNetlinkRouteRequest(syscall.RTM_GETADDR)
+	if err != nil {
+		return fmt.Errorf("RTM_GETADDR failed: %v", err)
+	}
+
+	return ExtractHostInterfaces(links, addrs, s.interfaces, s.interfaceAddrs)
+}
+
+func doNetlinkRouteRequest(req int) ([]syscall.NetlinkMessage, error) {
+	data, err := syscall.NetlinkRIB(req, syscall.AF_UNSPEC)
+	if err != nil {
+		return nil, err
+	}
+	return syscall.ParseNetlinkMessage(data)
+}
+
+func readTCPBufferSizeFile(filename string) (inet.TCPBufferSize, error) {
+	contents, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return inet.TCPBufferSize{}, fmt.Errorf("failed to read %s: %v", filename, err)
+	}
+	ioseq := usermem.BytesIOSequence(contents)
+	fields := make([]int32, 3)
+	if n, err := usermem.CopyInt32StringsInVec(context.Background(), ioseq.IO, ioseq.Addrs, fields, ioseq.Opts); n != ioseq.NumBytes() || err != nil {
+		return inet.TCPBufferSize{}, fmt.Errorf("failed to parse %s (%q): got %v after %d/%d bytes", filename, contents, err, n, ioseq.NumBytes())
+	}
+	return inet.TCPBufferSize{
+		Min:     int(fields[0]),
+		Default: int(fields[1]),
+		Max:     int(fields[2]),
+	}, nil
+}
+
+// Interfaces implements inet.Stack.Interfaces.
+func (s *Stack) Interfaces() map[int32]inet.Interface {
+	return s.interfaces
+}
+
+// InterfaceAddrs implements inet.Stack.InterfaceAddrs.
+func (s *Stack) InterfaceAddrs() map[int32][]inet.InterfaceAddr {
+	return s.interfaceAddrs
+}
+
+// SupportsIPv6 implements inet.Stack.SupportsIPv6.
+func (s *Stack) SupportsIPv6() bool {
+	return s.supportsIPv6
+}
+
+// TCPReceiveBufferSize implements inet.Stack.TCPReceiveBufferSize.
+func (s *Stack) TCPReceiveBufferSize() (inet.TCPBufferSize, error) {
+	return s.tcpRecvBufSize, nil
+}
+
+// SetTCPReceiveBufferSize implements inet.Stack.SetTCPReceiveBufferSize.
+func (s *Stack) SetTCPReceiveBufferSize(size inet.TCPBufferSize) error {
+	return syserror.EACCES
+}
+
+// TCPSendBufferSize implements inet.Stack.TCPSendBufferSize.
+func (s *Stack) TCPSendBufferSize() (inet.TCPBufferSize, error) {
+	return s.tcpSendBufSize, nil
+}
+
+// SetTCPSendBufferSize implements inet.Stack.SetTCPSendBufferSize.
+func (s *Stack) SetTCPSendBufferSize(size inet.TCPBufferSize) error {
+	return syserror.EACCES
+}
+
+// TCPSACKEnabled implements inet.Stack.TCPSACKEnabled.
+func (s *Stack) TCPSACKEnabled() (bool, error) {
+	return s.tcpSACKEnabled, nil
+}
+
+// SetTCPSACKEnabled implements inet.Stack.SetTCPSACKEnabled.
+func (s *Stack) SetTCPSACKEnabled(enabled bool) error {
+	return syserror.EACCES
+}