user50052: Let's say we have route of 3 hops A -> B -> C -> D (A pays D). And in the middle of payment (revealing secret R stage) node C disappear from network. In this case B will be not able to finalise payment because he don't know secret of hashlock.
I know that there is timelock, so most probably node B will need to start closing channel procedure (channel B -> C).
But what is happening with payment? Is it accepted/rejected/hanging? What is happening with A->B and C->D channels? Will they be hanging until situation with B->C is resolved? Or there is some kind of payment cancelation protocol?

user81940: The situation is less worse than you seem to assume. If node C disappears the channel A,B won't be affected. Also there is no direct need to affect the channel B, C and C, D. So most channels will stay open.
The payment process is a two stage process and it depends during which stage of the process node C disappears to see what happens and how nodes react. 
First stage: setting up htlcs from A to D. If C disappears before the htlcs have reached C the onion /payment is cancelled. No channel will be closed. Otherwise the resolution of the second stage takes place. 
Second stage: preimage is propagated. Node D might force close the channel to settle the htlc on chain. In that case B could also see the preimage on chain an settle off chain. C has time to come back and claim money from B. If C is away too long C will have lost money sich B will have won. If D has settled before C disappears C will not be incentivesed to disappear as C could not get Reimbursed by B.
So we see the only channel that might break in such a situation is the C,D channel. But in any cases only C can loose money / funds by disappearing. This C is Incentivised to stay online and be responsive

50052: <p>Let's say we have route of 3 hops A -> B -> C -> D (A pays D). And in the middle of payment (revealing secret R stage) node C disappear from network. In this case B will be not able to finalise payment because he don't know secret of hashlock.</p>

<p>I know that there is timelock, so most probably node B will need to start <code>closing channel</code> procedure (channel B -> C).</p>

<p>But what is happening with payment? Is it accepted/rejected/hanging? What is happening with A->B and C->D channels? Will they be hanging until situation with B->C is resolved? Or there is some kind of payment cancelation protocol?</p>
 81940: <p>The situation is less worse than you seem to assume. If node C disappears the channel A,B won't be affected. Also there is no direct need to affect the channel B, C and C, D. So most channels will stay open.</p>

<p>The payment process is a two stage process and it depends during which stage of the process node C disappears to see what happens and how nodes react. </p>

<p>First stage: setting up htlcs from A to D. If C disappears before the htlcs have reached C the onion /payment is cancelled. No channel will be closed. Otherwise the resolution of the second stage takes place. </p>

<p>Second stage: preimage is propagated. Node D might force close the channel to settle the htlc on chain. In that case B could also see the preimage on chain an settle off chain. C has time to come back and claim money from B. If C is away too long C will have lost money sich B will have won. If D has settled before C disappears C will not be incentivesed to disappear as C could not get Reimbursed by B.</p>

<p>So we see the only channel that might break in such a situation is the C,D channel. But in any cases only C can loose money / funds by disappearing. This C is Incentivised to stay online and be responsive</p>
