Lightning Network `channel_update` message Flag clarification












3















This is a lnd.log line:



2019-01-11 12:20:13.904 [DBG] PEER: Sending ChannelUpdate(chain_hash=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f, short_chan_id=601495532567724033, flag=256, update_time=2019-01-11 12:19:08 +0100 CET) to 46.229.165.136:9735


Since I cannot find a direct correlation with the spec at https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md
can someone clarify the "flag" value?



Where can I find the information below?



[1:message_flags]
[1:channel_flags]
[2:cltv_expiry_delta]
[8:htlc_minimum_msat]
[4:fee_base_msat]
[4:fee_proportional_millionths]
[8:htlc_maximum_msat] (option_channel_htlc_max)


Are they encoded in some way in this "flag"? How?










share|improve this question





























    3















    This is a lnd.log line:



    2019-01-11 12:20:13.904 [DBG] PEER: Sending ChannelUpdate(chain_hash=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f, short_chan_id=601495532567724033, flag=256, update_time=2019-01-11 12:19:08 +0100 CET) to 46.229.165.136:9735


    Since I cannot find a direct correlation with the spec at https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md
    can someone clarify the "flag" value?



    Where can I find the information below?



    [1:message_flags]
    [1:channel_flags]
    [2:cltv_expiry_delta]
    [8:htlc_minimum_msat]
    [4:fee_base_msat]
    [4:fee_proportional_millionths]
    [8:htlc_maximum_msat] (option_channel_htlc_max)


    Are they encoded in some way in this "flag"? How?










    share|improve this question



























      3












      3








      3








      This is a lnd.log line:



      2019-01-11 12:20:13.904 [DBG] PEER: Sending ChannelUpdate(chain_hash=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f, short_chan_id=601495532567724033, flag=256, update_time=2019-01-11 12:19:08 +0100 CET) to 46.229.165.136:9735


      Since I cannot find a direct correlation with the spec at https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md
      can someone clarify the "flag" value?



      Where can I find the information below?



      [1:message_flags]
      [1:channel_flags]
      [2:cltv_expiry_delta]
      [8:htlc_minimum_msat]
      [4:fee_base_msat]
      [4:fee_proportional_millionths]
      [8:htlc_maximum_msat] (option_channel_htlc_max)


      Are they encoded in some way in this "flag"? How?










      share|improve this question
















      This is a lnd.log line:



      2019-01-11 12:20:13.904 [DBG] PEER: Sending ChannelUpdate(chain_hash=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f, short_chan_id=601495532567724033, flag=256, update_time=2019-01-11 12:19:08 +0100 CET) to 46.229.165.136:9735


      Since I cannot find a direct correlation with the spec at https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md
      can someone clarify the "flag" value?



      Where can I find the information below?



      [1:message_flags]
      [1:channel_flags]
      [2:cltv_expiry_delta]
      [8:htlc_minimum_msat]
      [4:fee_base_msat]
      [4:fee_proportional_millionths]
      [8:htlc_maximum_msat] (option_channel_htlc_max)


      Are they encoded in some way in this "flag"? How?







      lightning-network lightning-network-daemon lightning-rfc channels






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Jan 11 at 19:01









      cdecker

      7,04812954




      7,04812954










      asked Jan 11 at 16:16









      Stefano AngieriStefano Angieri

      254




      254






















          1 Answer
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          4














          The flags field (2 bytes) has been split into two different (1 byte) fields, the message_flags (most significant bits) and the channel_flags field (least significant bits). Hence the flags value displayed in lnd has the message_flags byte set to 0x00 and the message_flags set to 0x01.



          message_flags indicates that this channel_update has some optional fields appended to the end. In this case it has the 0th bit set, which corresponds to the option_channel_htlc_max option, hence the channel_update has an additional field htlc_maximum_msat appended.






          share|improve this answer
























          • So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

            – Stefano Angieri
            Jan 15 at 11:31













          • Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

            – cdecker
            Jan 15 at 12:55











          Your Answer








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          active

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          4














          The flags field (2 bytes) has been split into two different (1 byte) fields, the message_flags (most significant bits) and the channel_flags field (least significant bits). Hence the flags value displayed in lnd has the message_flags byte set to 0x00 and the message_flags set to 0x01.



          message_flags indicates that this channel_update has some optional fields appended to the end. In this case it has the 0th bit set, which corresponds to the option_channel_htlc_max option, hence the channel_update has an additional field htlc_maximum_msat appended.






          share|improve this answer
























          • So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

            – Stefano Angieri
            Jan 15 at 11:31













          • Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

            – cdecker
            Jan 15 at 12:55
















          4














          The flags field (2 bytes) has been split into two different (1 byte) fields, the message_flags (most significant bits) and the channel_flags field (least significant bits). Hence the flags value displayed in lnd has the message_flags byte set to 0x00 and the message_flags set to 0x01.



          message_flags indicates that this channel_update has some optional fields appended to the end. In this case it has the 0th bit set, which corresponds to the option_channel_htlc_max option, hence the channel_update has an additional field htlc_maximum_msat appended.






          share|improve this answer
























          • So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

            – Stefano Angieri
            Jan 15 at 11:31













          • Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

            – cdecker
            Jan 15 at 12:55














          4












          4








          4







          The flags field (2 bytes) has been split into two different (1 byte) fields, the message_flags (most significant bits) and the channel_flags field (least significant bits). Hence the flags value displayed in lnd has the message_flags byte set to 0x00 and the message_flags set to 0x01.



          message_flags indicates that this channel_update has some optional fields appended to the end. In this case it has the 0th bit set, which corresponds to the option_channel_htlc_max option, hence the channel_update has an additional field htlc_maximum_msat appended.






          share|improve this answer













          The flags field (2 bytes) has been split into two different (1 byte) fields, the message_flags (most significant bits) and the channel_flags field (least significant bits). Hence the flags value displayed in lnd has the message_flags byte set to 0x00 and the message_flags set to 0x01.



          message_flags indicates that this channel_update has some optional fields appended to the end. In this case it has the 0th bit set, which corresponds to the option_channel_htlc_max option, hence the channel_update has an additional field htlc_maximum_msat appended.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Jan 11 at 19:08









          cdeckercdecker

          7,04812954




          7,04812954













          • So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

            – Stefano Angieri
            Jan 15 at 11:31













          • Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

            – cdecker
            Jan 15 at 12:55



















          • So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

            – Stefano Angieri
            Jan 15 at 11:31













          • Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

            – cdecker
            Jan 15 at 12:55

















          So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

          – Stefano Angieri
          Jan 15 at 11:31







          So Basically the "Flag" is a 16 bits field [8 bit message_flag + 8 bit channel_flags]. Is it possible to find the others information [cltv_expiry_delta, htlc_minimum_msat, fee_base_msat, fee_proportional_millionths, htlc_maximum_msat] exploring the log or it is only possible by using the lncli getchainifo? How can a Node, receiving a channel update message, understand and set the new channel policies?

          – Stefano Angieri
          Jan 15 at 11:31















          Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

          – cdecker
          Jan 15 at 12:55





          Not too familiar with the lnd RPC interface, I mostly work on c-lightning. But I guess it should list those with peers as well. And you can set all of these parameters on startup using cli options.

          – cdecker
          Jan 15 at 12:55


















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