109 lines
2.9 KiB
Go
109 lines
2.9 KiB
Go
package packet
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import (
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"context"
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"net/netip"
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"github.com/rs/zerolog"
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)
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// ICMPRouter sends ICMP messages and listens for their responses
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type ICMPRouter interface {
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// Serve starts listening for responses to the requests until context is done
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Serve(ctx context.Context) error
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// Request sends an ICMP message. Implementations should not modify pk after the function returns.
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Request(pk *ICMP, responder FunnelUniPipe) error
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}
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// Upstream of raw packets
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type Upstream interface {
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// ReceivePacket waits for the next raw packet from upstream
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ReceivePacket(ctx context.Context) (RawPacket, error)
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}
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// Router routes packets between Upstream and ICMPRouter. Currently it rejects all other type of ICMP packets
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type Router struct {
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upstream Upstream
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returnPipe FunnelUniPipe
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globalConfig *GlobalRouterConfig
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logger *zerolog.Logger
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checkRouterEnabledFunc func() bool
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}
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// GlobalRouterConfig is the configuration shared by all instance of Router.
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type GlobalRouterConfig struct {
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ICMPRouter ICMPRouter
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IPv4Src netip.Addr
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IPv6Src netip.Addr
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Zone string
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}
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func NewRouter(globalConfig *GlobalRouterConfig, upstream Upstream, returnPipe FunnelUniPipe, logger *zerolog.Logger, checkRouterEnabledFunc func() bool) *Router {
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return &Router{
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upstream: upstream,
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returnPipe: returnPipe,
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globalConfig: globalConfig,
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logger: logger,
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checkRouterEnabledFunc: checkRouterEnabledFunc,
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}
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}
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func (r *Router) Serve(ctx context.Context) error {
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icmpDecoder := NewICMPDecoder()
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encoder := NewEncoder()
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for {
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rawPacket, err := r.upstream.ReceivePacket(ctx)
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if err != nil {
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return err
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}
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// Drop packets if ICMPRouter wasn't created
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if r.globalConfig == nil {
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continue
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}
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if enabled := r.checkRouterEnabledFunc(); !enabled {
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continue
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}
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icmpPacket, err := icmpDecoder.Decode(rawPacket)
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if err != nil {
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r.logger.Err(err).Msg("Failed to decode ICMP packet from quic datagram")
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continue
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}
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if icmpPacket.TTL <= 1 {
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if err := r.sendTTLExceedMsg(icmpPacket, rawPacket, encoder); err != nil {
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r.logger.Err(err).Msg("Failed to return ICMP TTL exceed error")
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}
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continue
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}
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icmpPacket.TTL--
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if err := r.globalConfig.ICMPRouter.Request(icmpPacket, r.returnPipe); err != nil {
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r.logger.Err(err).
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Str("src", icmpPacket.Src.String()).
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Str("dst", icmpPacket.Dst.String()).
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Interface("type", icmpPacket.Type).
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Msg("Failed to send ICMP packet")
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continue
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}
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}
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}
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func (r *Router) sendTTLExceedMsg(pk *ICMP, rawPacket RawPacket, encoder *Encoder) error {
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var srcIP netip.Addr
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if pk.Dst.Is4() {
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srcIP = r.globalConfig.IPv4Src
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} else {
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srcIP = r.globalConfig.IPv6Src
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}
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ttlExceedPacket := NewICMPTTLExceedPacket(pk.IP, rawPacket, srcIP)
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encodedTTLExceed, err := encoder.Encode(ttlExceedPacket)
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if err != nil {
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return err
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}
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return r.returnPipe.SendPacket(pk.Src, encodedTTLExceed)
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}
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