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|
package bgp
import (
"encoding/binary"
"fmt"
"net"
"strconv"
)
// Validator for BGPUpdate
func ValidateUpdateMsg(m *BGPUpdate, rfs map[RouteFamily]bool) (bool, error) {
eCode := uint8(BGP_ERROR_UPDATE_MESSAGE_ERROR)
eSubCodeAttrList := uint8(BGP_ERROR_SUB_MALFORMED_ATTRIBUTE_LIST)
eSubCodeMissing := uint8(BGP_ERROR_SUB_MISSING_WELL_KNOWN_ATTRIBUTE)
if len(m.NLRI) > 0 || len(m.WithdrawnRoutes) > 0 {
if _, ok := rfs[RF_IPv4_UC]; !ok {
return false, NewMessageError(0, 0, nil, fmt.Sprintf("Address-family rf %d not avalible for session", RF_IPv4_UC))
}
}
seen := make(map[BGPAttrType]PathAttributeInterface)
// check path attribute
for _, a := range m.PathAttributes {
// check duplication
if _, ok := seen[a.getType()]; !ok {
seen[a.getType()] = a
} else {
eMsg := "the path attribute apears twice. Type : " + strconv.Itoa(int(a.getType()))
return false, NewMessageError(eCode, eSubCodeAttrList, nil, eMsg)
}
//check specific path attribute
ok, e := ValidateAttribute(a, rfs)
if !ok {
return false, e
}
}
if len(m.NLRI) > 0 {
// check the existence of well-known mandatory attributes
exist := func(attrs []BGPAttrType) (bool, BGPAttrType) {
for _, attr := range attrs {
_, ok := seen[attr]
if !ok {
return false, attr
}
}
return true, 0
}
mandatory := []BGPAttrType{BGP_ATTR_TYPE_ORIGIN, BGP_ATTR_TYPE_AS_PATH, BGP_ATTR_TYPE_NEXT_HOP}
if ok, t := exist(mandatory); !ok {
eMsg := "well-known mandatory attributes are not present. type : " + strconv.Itoa(int(t))
data := []byte{byte(t)}
return false, NewMessageError(eCode, eSubCodeMissing, data, eMsg)
}
}
return true, nil
}
func ValidateAttribute(a PathAttributeInterface, rfs map[RouteFamily]bool) (bool, error) {
eCode := uint8(BGP_ERROR_UPDATE_MESSAGE_ERROR)
eSubCodeBadOrigin := uint8(BGP_ERROR_SUB_INVALID_ORIGIN_ATTRIBUTE)
eSubCodeBadNextHop := uint8(BGP_ERROR_SUB_INVALID_NEXT_HOP_ATTRIBUTE)
eSubCodeUnknown := uint8(BGP_ERROR_SUB_UNRECOGNIZED_WELL_KNOWN_ATTRIBUTE)
checkPrefix := func(l []AddrPrefixInterface) bool {
for _, prefix := range l {
rf := AfiSafiToRouteFamily(prefix.AFI(), prefix.SAFI())
if _, ok := rfs[rf]; !ok {
return false
}
}
return true
}
switch p := a.(type) {
case *PathAttributeMpUnreachNLRI:
rf := AfiSafiToRouteFamily(p.AFI, p.SAFI)
if _, ok := rfs[rf]; !ok {
return false, NewMessageError(0, 0, nil, fmt.Sprintf("Address-family rf %d not avalible for session", rf))
}
if checkPrefix(p.Value) == false {
return false, NewMessageError(0, 0, nil, fmt.Sprintf("Address-family rf %d not avalible for session", rf))
}
case *PathAttributeMpReachNLRI:
rf := AfiSafiToRouteFamily(p.AFI, p.SAFI)
if _, ok := rfs[rf]; !ok {
return false, NewMessageError(0, 0, nil, fmt.Sprintf("Address-family rf %d not avalible for session", rf))
}
if checkPrefix(p.Value) == false {
return false, NewMessageError(0, 0, nil, fmt.Sprintf("Address-family rf %d not avalible for session", rf))
}
case *PathAttributeOrigin:
v := uint8(p.Value[0])
if v != BGP_ORIGIN_ATTR_TYPE_IGP &&
v != BGP_ORIGIN_ATTR_TYPE_EGP &&
v != BGP_ORIGIN_ATTR_TYPE_INCOMPLETE {
data, _ := a.Serialize()
eMsg := "invalid origin attribute. value : " + strconv.Itoa(int(v))
return false, NewMessageError(eCode, eSubCodeBadOrigin, data, eMsg)
}
case *PathAttributeNextHop:
isZero := func(ip net.IP) bool {
res := ip[0] & 0xff
return res == 0x00
}
isClassDorE := func(ip net.IP) bool {
res := ip[0] & 0xe0
return res == 0xe0
}
//check IP address represents host address
if p.Value.IsLoopback() || isZero(p.Value) || isClassDorE(p.Value) {
eMsg := "invalid nexthop address"
data, _ := a.Serialize()
return false, NewMessageError(eCode, eSubCodeBadNextHop, data, eMsg)
}
case *PathAttributeUnknown:
if p.getFlags()&BGP_ATTR_FLAG_OPTIONAL == 0 {
eMsg := "unrecognized well-known attribute"
data, _ := a.Serialize()
return false, NewMessageError(eCode, eSubCodeUnknown, data, eMsg)
}
}
return true, nil
}
// validator for PathAttribute
func ValidateFlags(t BGPAttrType, flags uint8) (bool, string) {
/*
* RFC 4271 P.17 For well-known attributes, the Transitive bit MUST be set to 1.
*/
if flags&BGP_ATTR_FLAG_OPTIONAL == 0 && flags&BGP_ATTR_FLAG_TRANSITIVE == 0 {
eMsg := "well-known attribute must have transitive flag 1"
return false, eMsg
}
/*
* RFC 4271 P.17 For well-known attributes and for optional non-transitive attributes,
* the Partial bit MUST be set to 0.
*/
if flags&BGP_ATTR_FLAG_OPTIONAL == 0 && flags&BGP_ATTR_FLAG_PARTIAL != 0 {
eMsg := "well-known attribute must have partial bit 0"
return false, eMsg
}
if flags&BGP_ATTR_FLAG_OPTIONAL != 0 && flags&BGP_ATTR_FLAG_TRANSITIVE == 0 && flags&BGP_ATTR_FLAG_PARTIAL != 0 {
eMsg := "optional non-transitive attribute must have partial bit 0"
return false, eMsg
}
// check flags are correct
if f, ok := pathAttrFlags[t]; ok {
if f != (flags & ^uint8(BGP_ATTR_FLAG_EXTENDED_LENGTH)) {
eMsg := "flags are invalid. attribtue type : " + strconv.Itoa(int(t))
return false, eMsg
}
}
return true, ""
}
func ValidateBGPMessage(m *BGPMessage) error {
if m.Header.Len > BGP_MAX_MESSAGE_LENGTH {
buf := make([]byte, 2)
binary.BigEndian.PutUint16(buf, m.Header.Len)
return NewMessageError(BGP_ERROR_MESSAGE_HEADER_ERROR, BGP_ERROR_SUB_BAD_MESSAGE_LENGTH, buf, "too long length")
}
return nil
}
func ValidateOpenMsg(m *BGPOpen, expectedAS uint32) error {
if m.Version != 4 {
return NewMessageError(BGP_ERROR_OPEN_MESSAGE_ERROR, BGP_ERROR_SUB_UNSUPPORTED_VERSION_NUMBER, nil, fmt.Sprintf("upsuppored version %d", m.Version))
}
as := uint32(m.MyAS)
for _, p := range m.OptParams {
paramCap, y := p.(*OptionParameterCapability)
if !y {
continue
}
for _, c := range paramCap.Capability {
if c.Code() == BGP_CAP_FOUR_OCTET_AS_NUMBER {
cap := c.(*CapFourOctetASNumber)
as = cap.CapValue
}
}
}
if as != expectedAS {
return NewMessageError(BGP_ERROR_OPEN_MESSAGE_ERROR, BGP_ERROR_SUB_BAD_PEER_AS, nil, fmt.Sprintf("as number mismatch expected %d, received %d", expectedAS, as))
}
if m.HoldTime < 3 && m.HoldTime != 0 {
return NewMessageError(BGP_ERROR_OPEN_MESSAGE_ERROR, BGP_ERROR_SUB_UNACCEPTABLE_HOLD_TIME, nil, fmt.Sprintf("unacceptable hold time %d", m.HoldTime))
}
return nil
}
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