Add drop reason example#7
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vbnogueira
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| @@ -0,0 +1,254 @@ | |||
| # digest | |||
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I am tempted to call this: drop_reason instead of digest. Then the opening statement here is:
This program demonstrates how to capture events from the datapath and logging them as events to the control plane. In this case we capture the reason why packets are dropped, what port they arrived on and what src mac address was observed on the packet. Packets could be dropped for two reasons:
- the parser was unable to parse the packet
- unable to find a matching entry on lookup of table nh_table.
| rejected. After the parser recognizes an ipv4 packet, the src ip address is used as a lookup | ||
| key for table *nh_table*. On a table hit, the programmed action *send_nh(port, srcMac, dstMac)* instance is executed. | ||
| The action first sets the src and destination mac address, then redirects the packet to a specified port, sets the ingress_port, sets `send_digest` to true and redirects the packet. On a table miss the packet is simply dropped. | ||
| `my_ingress_metadata_t` will hold the port on where the packet arrived and `send_digest`. `send_digest` signals to the deparser to send a digest message to user space. This digest message will hold the source mac address and the port where the packet arrived: |
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s/dropped/dropped and event sent to the control plane with reason set to blah
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| run TC monitor for digest events: | ||
| `$TC mon p4 digest` | ||
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We need to see the events here..
| Compile the parser and control blocks programs if you have not already | ||
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| `make` | ||
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Shouldnt you compile first before you modprobe?
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It doesn't matter
I can modprobe before or after
| `ping -I p4port0 10.0.1.2 -c 1` | ||
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| Let's check some stats, below shows 3 packets dropped by the parser on <u>terminal 3</u>: | ||
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Shouldnt you point the user to terminal 2 at this point? And what they should expect to see?
And what was the packet dropped by the parser.
You are literally cutting and pasting other examples i had without thinking through what useful information is needed for the user..
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That's why I transformed it into a draft, because I needed to fix it given the new semantic
It's just copied and pasted at this point, I'm fixing and testing it before making the PR ready for review
| # digest | ||
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| The *digest* program first parses ethernet <u>ipv4</u> packets. Any other packets are | ||
| rejected. After the parser recognizes an ipv4 packet, the src ip address is used as a lookup |
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s/rejected/rejected and event blah blah sent to the control plane.
| parser_rejected = 1, | ||
| table_miss = 2 | ||
| }; | ||
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Should the DROP_REASON be capitalized?
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I think that would work also
| "bitwidth" : 8 | ||
| } | ||
| ] | ||
| } |
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We need the drop reason not as a number but as a name for human consumption. Maybe i am missing something.
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We discussed offline and what we'd like would be for the compiler to emit in the JSON the mapping from integer to corresponding enum string (parser_rejected or table_miss)
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Add drop reason example that drops a packet, and sends a digest message containing the ingress port (port where the packet arrived), the src mac address and the drop reason (PARSER_REJECTED or TABLE_MISS) If the packet is not dropped, it will be redirected
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Add drop reason example that drops a packet, and sends a digest message
containing the ingress port (port where the packet arrived), the src
mac address and the drop reason (PARSER_REJECTED or TABLE_MISS)
If the packet is not dropped, it will be redirected