Merge pull request #136 from nvksie/icmp_id_bpf_filter

filter icmp id with sock_filter, to optimize rawsocket preformance

packetconn.go

@@ -23,6 +23,7 @@ type packetConn interface {
 	SetBroadcastFlag() error
 	SetIfIndex(ifIndex int)
 	SetTrafficClass(uint8) error
+	InstallICMPIDFilter(id int) error
 }
 
 type icmpConn struct {

ping.go

@@ -979,6 +979,13 @@ func (p *Pinger) listen() (packetConn, error) {
 		p.Stop()
 		return nil, err
 	}
+
+	if p.Privileged() {
+		if err := conn.InstallICMPIDFilter(p.id); err != nil {
+			p.logger.Warnf("error installing icmp filter, %v", err)
+		}
+	}
+
 	return conn, nil
 }
 

ping_test.go

@@ -677,6 +677,7 @@ func (c testPacketConn) SetTTL(t int)                      {}
 func (c testPacketConn) SetMark(m uint) error              { return nil }
 func (c testPacketConn) SetDoNotFragment() error           { return nil }
 func (c testPacketConn) SetBroadcastFlag() error           { return nil }
+func (c testPacketConn) InstallICMPIDFilter(id int) error  { return nil }
 func (c testPacketConn) SetIfIndex(ifIndex int)            {}
 func (c testPacketConn) SetTrafficClass(uint8) error       { return nil }
 

utils_linux.go

@@ -9,7 +9,10 @@ import (
 	"reflect"
 	"syscall"
 
+	"golang.org/x/net/bpf"
 	"golang.org/x/net/icmp"
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
 )
 
 // Returns the length of an ICMP message.
@@ -137,6 +140,41 @@ func (c *icmpV6Conn) SetBroadcastFlag() error {
 	)
 }
 
+// InstallICMPIDFilter attaches a BPF program to the connection to filter ICMP packets id.
+func (c *icmpv4Conn) InstallICMPIDFilter(id int) error {
+	filter, err := bpf.Assemble([]bpf.Instruction{
+		bpf.LoadMemShift{Off: 0},          // Skip IP header
+		bpf.LoadIndirect{Off: 4, Size: 2}, // Load ICMP echo ident
+		bpf.JumpIf{Cond: bpf.JumpEqual, Val: uint32(id), SkipTrue: 0, SkipFalse: 1},                     // Jump on ICMP Echo Request (ID check)
+		bpf.RetConstant{Val: ^uint32(0)},                                                                // If our ID, accept the packet
+		bpf.LoadIndirect{Off: 0, Size: 1},                                                               // Load ICMP type
+		bpf.JumpIf{Cond: bpf.JumpEqual, Val: uint32(ipv4.ICMPTypeEchoReply), SkipTrue: 1, SkipFalse: 0}, // Check if ICMP Echo Reply
+		bpf.RetConstant{Val: 0xFFFFFFF},                                                                 // Accept packet if it's not Echo Reply
+		bpf.RetConstant{Val: 0},                                                                         // Reject Echo packet with wrong identifier
+	})
+	if err != nil {
+		return err
+	}
+	return c.c.IPv4PacketConn().SetBPF(filter)
+}
+
+// InstallICMPIDFilter attaches a BPF program to the connection to filter ICMPv6 packets id.
+func (c *icmpV6Conn) InstallICMPIDFilter(id int) error {
+	filter, err := bpf.Assemble([]bpf.Instruction{
+		bpf.LoadAbsolute{Off: 4, Size: 2},                                                               // Load ICMP echo identifier
+		bpf.JumpIf{Cond: bpf.JumpEqual, Val: uint32(id), SkipTrue: 0, SkipFalse: 1},                     // Check if it matches our identifier
+		bpf.RetConstant{Val: ^uint32(0)},                                                                // Accept if true
+		bpf.LoadAbsolute{Off: 0, Size: 1},                                                               // Load ICMP type
+		bpf.JumpIf{Cond: bpf.JumpEqual, Val: uint32(ipv6.ICMPTypeEchoReply), SkipTrue: 1, SkipFalse: 0}, // Check if it is an ICMP6 echo reply
+		bpf.RetConstant{Val: ^uint32(0)},                                                                // Accept if false
+		bpf.RetConstant{Val: 0},                                                                         // Reject if echo with wrong identifier
+	})
+	if err != nil {
+		return err
+	}
+	return c.c.IPv6PacketConn().SetBPF(filter)
+}
+
 // getFD gets the system file descriptor for an icmp.PacketConn
 func getFD(c *icmp.PacketConn) (uintptr, error) {
 	v := reflect.ValueOf(c).Elem().FieldByName("c").Elem()

utils_other.go

@@ -58,3 +58,11 @@ func (c *icmpv4Conn) SetBroadcastFlag() error {
 func (c *icmpV6Conn) SetBroadcastFlag() error {
 	return nil
 }
+
+func (c *icmpv4Conn) InstallICMPIDFilter(id int) error {
+	return nil
+}
+
+func (c *icmpV6Conn) InstallICMPIDFilter(id int) error {
+	return nil
+}

utils_windows.go

@@ -86,3 +86,11 @@ func (c *icmpv4Conn) SetBroadcastFlag() error {
 func (c *icmpV6Conn) SetBroadcastFlag() error {
 	return nil
 }
+
+func (c *icmpv4Conn) InstallICMPIDFilter(id int) error {
+	return nil
+}
+
+func (c *icmpV6Conn) InstallICMPIDFilter(id int) error {
+	return nil
+}