How does relayer know where to get the packet? #183
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As far as I know, chain stores the |
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Replies: 2 comments 4 replies
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By design, the relayer doesn't know what the packet is about, and doesn't need to. This is analogous to the IP protocol: you don't need to know what the data is about to route the packet to the destination. Intuitively, all the relayer does is send the packet data to the destination chain (on the appropriate channel/port), along with a proof that the packet really was sent by the sending chain. The destination chain then convinces itself that the packet really was sent (by checking the proof), and gives the packet data to the appropriate IBC module (i.e. bound to the destination port), e.g. the ICS-20 transfer module. In this example, the transfer module is the component that knows how to interpret the packet data. Hopefully that gives an intuition as to why the relayer doesn't need any information about what the packet data is in order to do its jobs of relaying. Does that fully answer your question though? |
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Thanks for your reply. I'm sorry, I didn't express myself clearly.
Yes, relayer does not care about what the packet data is about. |
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That's right; the packet binary data is stored in events (e.g. SendPacket event), which are sent back to tendermint in deliverTx response. The relayer gets the binary packet data from there.
We need to distinguish between what is stored "on-chain" (the packet commitments) and "off-chain" by the tendermint node (events and more, making these available to relayers). |
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Thanks! |
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Is this description accurate? |
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That's right. The relayer gets the packet data from the event, and needs to fetch the proof that the packet commitment was indeed stored at the expected location. Here is the code that does that. |
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By design, the relayer doesn't know what the packet is about, and doesn't need to. This is analogous to the IP protocol: you don't need to know what the data is about to route the packet to the destination.
Intuitively, all the relayer does is send the packet data to the destination chain (on the appropriate channel/port), along with a proof that the packet really was sent by the sending chain. The destination chain then convinces itself that the packet really was sent (by checking the proof), and gives the packet data to the appropriate IBC module (i.e. bound to the destination port), e.g. the ICS-20 transfer module. In this example, the transfer module is the component that knows how to…