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info_recordpath.go
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/
info_recordpath.go
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// Copyright 2018 ETH Zurich
//
// 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 scmp
import (
"bytes"
"fmt"
"time"
"github.com/scionproto/scion/go/lib/addr"
"github.com/scionproto/scion/go/lib/common"
)
// Record Path Entry format:
//
// 0B 1 2 3 4 5 6 7
// +--------+--------+--------+--------+--------+--------+--------+--------+
// | IA |
// +--------+--------+--------+--------+--------+--------+--------+--------+
// | IfID |
// +--------+--------+--------+--------+--------+--------+--------+--------+
// | TS | Unused |
// +--------+--------+--------+--------+--------+--------+--------+--------+
//
// TS is the time since SCMP Timestamp in microseconds, truncated to 32bits.
//
const (
recordPathEntryLen = addr.IABytes + 4 + common.IFIDBytes
)
type RecordPathEntry struct {
IA addr.IA
IfID common.IFIDType
TS uint32
}
func (entry *RecordPathEntry) write(b common.RawBytes) {
entry.IA.Write(b)
offset := addr.IABytes
common.Order.PutUint64(b[offset:], uint64(entry.IfID))
offset += 8
common.Order.PutUint32(b[offset:], entry.TS)
}
func (entry *RecordPathEntry) read(b common.RawBytes) {
entry.IA = addr.IAFromRaw(b)
offset := addr.IABytes
entry.IfID = common.IFIDType(common.Order.Uint64(b[offset:]))
offset += 8
entry.TS = common.Order.Uint32(b[offset:])
}
func (entry *RecordPathEntry) String() string {
return fmt.Sprintf("IA: %s, IfID: %d, TimeOff: %s", entry.IA, entry.IfID,
time.Duration(entry.TS)*time.Microsecond)
}
// Record Path packet format:
//
// 0B 1 2 3 4 5 6 7
// +--------+--------+--------+--------+--------+--------+--------+--------+
// | Id |
// +--------+--------+--------+--------+--------+--------+--------+--------+
// |NumHops | Unused |
// +--------+--------+--------+--------+--------+--------+--------+--------+
// | RecordPathEntry[0] |
// +--------+--------+--------+--------+--------+--------+--------+--------+
// . . .
// . . .
// . . .
// +--------+--------+--------+--------+--------+--------+--------+--------+
// | RecordPathEntry[n] |
// +--------+--------+--------+--------+--------+--------+--------+--------+
//
var _ Info = (*InfoRecordPath)(nil)
const (
recordPathHdrLen = 16
)
type InfoRecordPath struct {
Id uint64
Entries []*RecordPathEntry
}
func InfoRecordPathFromRaw(b common.RawBytes) (*InfoRecordPath, error) {
if len(b) < recordPathHdrLen {
return nil, common.NewBasicError("Truncated RecordPath info header", nil,
"min", recordPathHdrLen, "actual", len(b))
}
rec := &InfoRecordPath{}
rec.Id = common.Order.Uint64(b[:8])
numHops := int(b[8])
// Skip header
if len(b[recordPathHdrLen:])%recordPathEntryLen != 0 {
return nil, common.NewBasicError("Illegal RecordPath info entries length", nil,
"len", len(b[recordPathHdrLen:]), "entryLen", recordPathEntryLen)
}
maxHops := len(b[recordPathHdrLen:]) / recordPathEntryLen
if numHops > maxHops {
return nil, common.NewBasicError("Invalid header", nil, "NumHops", numHops,
"MaxHops", maxHops)
}
rec.Entries = make([]*RecordPathEntry, numHops, maxHops)
offset := recordPathHdrLen
for i := 0; i < numHops; i++ {
e := &RecordPathEntry{}
e.read(b[offset:])
rec.Entries[i] = e
offset += recordPathEntryLen
}
return rec, nil
}
func (rec *InfoRecordPath) Copy() Info {
r := &InfoRecordPath{Id: rec.Id}
r.Entries = make([]*RecordPathEntry, rec.NumHops(), rec.TotalHops())
for i, e := range rec.Entries {
r.Entries[i] = &RecordPathEntry{IA: e.IA, TS: e.TS, IfID: e.IfID}
}
return r
}
func (rec *InfoRecordPath) NumHops() int {
return len(rec.Entries)
}
func (rec *InfoRecordPath) TotalHops() int {
return cap(rec.Entries)
}
func (rec *InfoRecordPath) Len() int {
return recordPathHdrLen + rec.TotalHops()*recordPathEntryLen
}
func (rec *InfoRecordPath) Write(b common.RawBytes) (int, error) {
if len(b) < rec.Len() {
return 0, common.NewBasicError("Not enough space in buffer", nil,
"Expected", rec.Len(), "Actual", len(b))
}
common.Order.PutUint64(b[0:8], rec.Id)
b[8] = uint8(rec.NumHops())
offset := recordPathHdrLen
for _, e := range rec.Entries {
e.write(b[offset:])
offset += recordPathEntryLen
}
if offset < rec.Len() {
b[offset:].Zero()
}
return rec.Len(), nil
}
func (rec *InfoRecordPath) String() string {
buf := &bytes.Buffer{}
fmt.Fprintf(buf, "RecordPath Id 0x%016x: Hops filled/total: %d/%d\n",
rec.Id, rec.NumHops(), rec.TotalHops())
for i, e := range rec.Entries {
fmt.Fprintf(buf, " %2d. %s\n", i+1, e.String())
}
return buf.String()
}