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Allow caller-defined sinks for packet sniffing.

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PiperOrigin-RevId: 307053624
This commit is contained in:
Tamir Duberstein
2020-04-17 09:05:16 -07:00
committed by gVisor bot
parent b4de018a67
commit 6c225ea2d5
1 changed files with 18 additions and 20 deletions
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pkg/tcpip/link/sniffer/sniffer.go
+18 -20
View File
@@ -24,7 +24,6 @@ import (
"encoding/binary"
"fmt"
"io"
"os"
"sync/atomic"
"time"
@@ -41,12 +40,12 @@ import (
// LogPackets must be accessed atomically.
var LogPackets uint32 = 1
// LogPacketsToFile is a flag used to enable or disable logging packets to a
// pcap file. Valid values are 0 or 1. A file must have been specified when the
// LogPacketsToPCAP is a flag used to enable or disable logging packets to a
// pcap writer. Valid values are 0 or 1. A writer must have been specified when the
// sniffer was created for this flag to have effect.
//
// LogPacketsToFile must be accessed atomically.
var LogPacketsToFile uint32 = 1
// LogPacketsToPCAP must be accessed atomically.
var LogPacketsToPCAP uint32 = 1
var transportProtocolMinSizes map[tcpip.TransportProtocolNumber]int = map[tcpip.TransportProtocolNumber]int{
header.ICMPv4ProtocolNumber: header.IPv4MinimumSize,
@@ -58,7 +57,7 @@ var transportProtocolMinSizes map[tcpip.TransportProtocolNumber]int = map[tcpip.
type endpoint struct {
dispatcher stack.NetworkDispatcher
lower stack.LinkEndpoint
file *os.File
writer io.Writer
maxPCAPLen uint32
}
@@ -98,23 +97,22 @@ func writePCAPHeader(w io.Writer, maxLen uint32) error {
})
}
// NewWithFile creates a new sniffer link-layer endpoint. It wraps around
// another endpoint and logs packets and they traverse the endpoint.
// NewWithWriter creates a new sniffer link-layer endpoint. It wraps around
// another endpoint and logs packets as they traverse the endpoint.
//
// Packets can be logged to file in the pcap format. A sniffer created
// with this function will not emit packets using the standard log
// package.
// Packets are logged to writer in the pcap format. A sniffer created with this
// function will not emit packets using the standard log package.
//
// snapLen is the maximum amount of a packet to be saved. Packets with a length
// less than or equal too snapLen will be saved in their entirety. Longer
// less than or equal to snapLen will be saved in their entirety. Longer
// packets will be truncated to snapLen.
func NewWithFile(lower stack.LinkEndpoint, file *os.File, snapLen uint32) (stack.LinkEndpoint, error) {
if err := writePCAPHeader(file, snapLen); err != nil {
func NewWithWriter(lower stack.LinkEndpoint, writer io.Writer, snapLen uint32) (stack.LinkEndpoint, error) {
if err := writePCAPHeader(writer, snapLen); err != nil {
return nil, err
}
return &endpoint{
lower: lower,
file: file,
writer: writer,
maxPCAPLen: snapLen,
}, nil
}
@@ -171,21 +169,21 @@ func (e *endpoint) GSOMaxSize() uint32 {
}
func (e *endpoint) dumpPacket(prefix string, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
file := e.file
if file == nil && atomic.LoadUint32(&LogPackets) == 1 {
writer := e.writer
if writer == nil && atomic.LoadUint32(&LogPackets) == 1 {
first := pkt.Header.View()
if len(first) == 0 {
first = pkt.Data.First()
}
logPacket(prefix, protocol, first, gso)
}
if file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
if writer != nil && atomic.LoadUint32(&LogPacketsToPCAP) == 1 {
totalLength := pkt.Header.UsedLength() + pkt.Data.Size()
length := totalLength
if max := int(e.maxPCAPLen); length > max {
length = max
}
if err := binary.Write(file, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(totalLength))); err != nil {
if err := binary.Write(writer, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(totalLength))); err != nil {
panic(err)
}
write := func(b []byte) {
@@ -193,7 +191,7 @@ func (e *endpoint) dumpPacket(prefix string, gso *stack.GSO, protocol tcpip.Netw
b = b[:length]
}
for len(b) != 0 {
n, err := file.Write(b)
n, err := writer.Write(b)
if err != nil {
panic(err)
}