ovs: open source package ovs

Author: mdlayher

ovs/action.go

@@ -0,0 +1,340 @@
+package ovs
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// An actionParser is a parser for OVS flow actions.
+type actionParser struct {
+	r *bufio.Reader
+	s stack
+}
+
+// newActionParser creates a new actionParser which wraps the input
+// io.Reader.
+func newActionParser(r io.Reader) *actionParser {
+	return &actionParser{
+		r: bufio.NewReader(r),
+		s: make(stack, 0),
+	}
+}
+
+// eof is a sentinel rune for end of file.
+var eof = rune(0)
+
+// read reads a single rune from the wrapped io.Reader.  It returns eof
+// if no more runes are present.
+func (p *actionParser) read() rune {
+	ch, _, err := p.r.ReadRune()
+	if err != nil {
+		return eof
+	}
+	return ch
+}
+
+// Parse parses a slice of Actions using the wrapped io.Reader.  The raw
+// action strings are also returned for inspection if needed.
+func (p *actionParser) Parse() ([]Action, []string, error) {
+	var actions []Action
+	var raw []string
+
+	for {
+		a, r, err := p.parseAction()
+		if err != nil {
+			// No more actions remain
+			if err == io.EOF {
+				break
+			}
+
+			return nil, nil, err
+		}
+
+		actions = append(actions, a)
+		raw = append(raw, r)
+	}
+
+	return actions, raw, nil
+}
+
+// parseAction parses a single Action and its raw text from the wrapped
+// io.Reader.
+func (p *actionParser) parseAction() (Action, string, error) {
+	// Track runes encountered
+	var buf bytes.Buffer
+
+	for {
+		ch := p.read()
+
+		// If comma encountered and no open parentheses, at end of this
+		// action string
+		if ch == ',' && p.s.len() == 0 {
+			break
+		}
+
+		// If EOF encountered, at end of string
+		if ch == eof {
+			// If no items in buffer, end of this action
+			if buf.Len() == 0 {
+				return nil, "", io.EOF
+			}
+
+			// Parse action from buffer
+			break
+		}
+
+		// Track open and closing parentheses using a stack to ensure
+		// that they are appropriately matched
+		switch ch {
+		case '(':
+			p.s.push()
+		case ')':
+			p.s.pop()
+		}
+
+		_, _ = buf.WriteRune(ch)
+	}
+
+	// Found an unmatched set of parentheses
+	if p.s.len() > 0 {
+		return nil, "", fmt.Errorf("invalid action: %q", buf.String())
+	}
+
+	s := buf.String()
+	act, err := parseAction(s)
+	return act, s, err
+}
+
+// A stack is a basic stack with elements that have no value.
+type stack []struct{}
+
+// len returns the current length of the stack.
+func (s *stack) len() int {
+	return len(*s)
+}
+
+// push adds an element to the stack.
+func (s *stack) push() {
+	*s = append(*s, struct{}{})
+}
+
+// pop removes an element from the stack.
+func (s *stack) pop() {
+	*s = (*s)[:s.len()-1]
+}
+
+var (
+	// resubmitRe is the regex used to match the resubmit action
+	// with one or more of its parameters.
+	resubmitRe = regexp.MustCompile(`resubmit\((\d*),(\d*)\)`)
+
+	// ctRe is the regex used to match the ct action with its
+	// parameter list.
+	ctRe = regexp.MustCompile(`ct\((\S+)\)`)
+
+	// loadRe is the regex used to match the load action
+	// with its parameters.
+	loadRe = regexp.MustCompile(`load:(\S+)->(\S+)`)
+
+	// setFieldRe is the regex used to match the set_field action
+	// with its parameters.
+	setFieldRe = regexp.MustCompile(`set_field:(\S+)->(\S+)`)
+)
+
+// TODO(mdlayher): replace parsing regex with arguments parsers
+
+// parseAction creates an Action function from the input string.
+func parseAction(s string) (Action, error) {
+	// Simple actions which match a basic string
+	switch strings.ToLower(s) {
+	case actionDrop:
+		return Drop(), nil
+	case actionFlood:
+		return Flood(), nil
+	case actionInPort:
+		return InPort(), nil
+	case actionLocal:
+		return Local(), nil
+	case actionNormal:
+		return Normal(), nil
+	case actionStripVLAN:
+		return StripVLAN(), nil
+	}
+
+	// ActionCT, with its arguments
+	if ss := ctRe.FindAllStringSubmatch(s, 1); len(ss) > 0 && len(ss[0]) == 2 {
+		// Results are:
+		//  - full string
+		//  - arguments list
+		return ConnectionTracking(ss[0][1]), nil
+	}
+
+	// ActionModDataLinkDestination, with its hardware address.
+	if strings.HasPrefix(s, patModDataLinkDestination[:len(patModDataLinkDestination)-2]) {
+		var addr string
+		n, err := fmt.Sscanf(s, patModDataLinkDestination, &addr)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			mac, err := net.ParseMAC(addr)
+			if err != nil {
+				return nil, err
+			}
+
+			return ModDataLinkDestination(mac), nil
+		}
+	}
+
+	// ActionModDataLinkSource, with its hardware address.
+	if strings.HasPrefix(s, patModDataLinkSource[:len(patModDataLinkSource)-2]) {
+		var addr string
+		n, err := fmt.Sscanf(s, patModDataLinkSource, &addr)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			mac, err := net.ParseMAC(addr)
+			if err != nil {
+				return nil, err
+			}
+
+			return ModDataLinkSource(mac), nil
+		}
+	}
+
+	// ActionModNetworkDestination, with it hardware address
+	if strings.HasPrefix(s, patModNetworkDestination[:len(patModNetworkDestination)-2]) {
+		var ip string
+		n, err := fmt.Sscanf(s, patModNetworkDestination, &ip)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			ip4 := net.ParseIP(ip).To4()
+			if ip4 == nil {
+				return nil, fmt.Errorf("invalid IPv4 address: %s", ip)
+			}
+
+			return ModNetworkDestination(ip4), nil
+		}
+	}
+
+	// ActionModNetworkSource, with it hardware address
+	if strings.HasPrefix(s, patModNetworkSource[:len(patModNetworkSource)-2]) {
+		var ip string
+		n, err := fmt.Sscanf(s, patModNetworkSource, &ip)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			ip4 := net.ParseIP(ip).To4()
+			if ip4 == nil {
+				return nil, fmt.Errorf("invalid IPv4 address: %s", ip)
+			}
+
+			return ModNetworkSource(ip4), nil
+		}
+	}
+
+	// ActionModTransportDestinationPort, with its port.
+	if strings.HasPrefix(s, patModTransportDestinationPort[:len(patModTransportDestinationPort)-2]) {
+		var port uint16
+		n, err := fmt.Sscanf(s, patModTransportDestinationPort, &port)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			return ModTransportDestinationPort(port), nil
+		}
+	}
+
+	// ActionModTransportSourcePort, with its port.
+	if strings.HasPrefix(s, patModTransportSourcePort[:len(patModTransportSourcePort)-2]) {
+		var port uint16
+		n, err := fmt.Sscanf(s, patModTransportSourcePort, &port)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			return ModTransportSourcePort(port), nil
+		}
+	}
+
+	// ActionModVLANVID, with its VLAN ID
+	if strings.HasPrefix(s, patModVLANVID[:len(patModVLANVID)-2]) {
+		var vlan int
+		n, err := fmt.Sscanf(s, patModVLANVID, &vlan)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			return ModVLANVID(vlan), nil
+		}
+	}
+
+	// ActionOutput, with its port number
+	if strings.HasPrefix(s, patOutput[:len(patOutput)-2]) {
+		var port int
+		n, err := fmt.Sscanf(s, patOutput, &port)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			return Output(port), nil
+		}
+	}
+
+	// ActionResubmit, with one or both of port number and table number
+	if ss := resubmitRe.FindAllStringSubmatch(s, 2); len(ss) > 0 && len(ss[0]) == 3 {
+		var (
+			port  int
+			table int
+
+			err error
+		)
+
+		// Results are:
+		//  - full string
+		//  - port
+		//  - table
+		if s := ss[0][1]; s != "" {
+			port, err = strconv.Atoi(s)
+			if err != nil {
+				return nil, err
+			}
+		}
+		if s := ss[0][2]; s != "" {
+			table, err = strconv.Atoi(ss[0][2])
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		return Resubmit(port, table), nil
+	}
+
+	if ss := loadRe.FindAllStringSubmatch(s, 2); len(ss) > 0 && len(ss[0]) == 3 {
+		// Results are:
+		//  - full string
+		//  - value
+		//  - field
+		return Load(ss[0][1], ss[0][2]), nil
+	}
+
+	if ss := setFieldRe.FindAllStringSubmatch(s, 2); len(ss) > 0 && len(ss[0]) == 3 {
+		// Results are:
+		//  - full string
+		//  - value
+		//  - field
+		return SetField(ss[0][1], ss[0][2]), nil
+	}
+
+	return nil, fmt.Errorf("no action matched for %q", s)
+}