user89634: 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? 

user120: 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.

89634: <p>This is a lnd.log line:</p>

<pre><code>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
</code></pre>

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

<p>Where can I find the information below?</p>

<pre><code>[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)
</code></pre>

<p>Are they encoded in some way in this "flag"? How? </p>
 120: <p>The <code>flags</code> field (2 bytes) has been split into two different (1 byte) fields, the <code>message_flags</code> (most significant bits) and the <code>channel_flags</code> field (least significant bits). Hence the flags value displayed in <code>lnd</code> has the <code>message_flags</code> byte set to <code>0x00</code> and the <code>message_flags</code> set to <code>0x01</code>.</p>

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