inetdiag.Parse and message cache

[gfr10598]

Adds basic inet message and attribute parsing, and a message cache.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 108

• 59 of 65 (90.77%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 90.033%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
inetdiag/inetdiag.go	40	46	86.96%

Totals
Change from base Build 83:	0.08%
Covered Lines:	271
Relevant Lines:	301

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💛 - Coveralls

[pboothe]

, small comments.

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Review status: 0 of 7 files reviewed at latest revision, all discussions resolved.

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cache/cache.go, line 22 at r2 (raw file):

	// Map from inode to ParsedMessage
	current map[uint32]*inetdiag.ParsedMessage
	past    map[uint32]*inetdiag.ParsedMessage

"stale" might be better than "past". It doesn't contain the inodes from the last round of updates, it contains the inodes from the last round that did not get updated this round.

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cache/cache.go, line 31 at r2 (raw file):

}

// Update swaps msg with the cache contents, and returns the cached value.

...and returns the evicted value from the cache.

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inetdiag/inetdiag_test.go, line 155 at r2 (raw file):

func TestParseGarbage(t *testing.T) {
	var json1 = `{"Header":{"Len":356,"Type":20,"Flags":2,"Seq":1,"Pid":148940},"Data":"CgEAAOpWE6cmIAAAEAMEFbM+nWqBv4ehJgf4sEANDAoAAAAAAAAAgQAAAAAdWwAAAAAAAAAAAAAAAAAAAAAAAAAAAAC13zIBBQAIAAAAAAAFAAUAIAAAAAUABgAgAAAAFAABAAAAAAAAAAAAAAAAAAAAAAAoAAcAAAAAAICiBQAAAAAAALQAAAAAAAAAAAAAAAAAAAAAAAAAAAAArAACAAEAAAAAB3gBQIoDAECcAABEBQAAuAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAUCEAAAAAAAAgIQAAQCEAANwFAACsywIAJW8AAIRKAAD///9/CgAAAJQFAAADAAAALMkAAIBwAAAAAAAALnUOAAAAAAD///////////ayBAAAAAAASfQPAAAAAADMEQAANRMAAAAAAABiNQAAxAsAAGMIAABX5AUAAAAAAAoABABjdWJpYwAAAA=="}`

I can't tell the difference between the good input data and the bad input data. Is that okay? Maybe. But I thought I should let you know.

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Comments from Reviewable

[gfr10598]

Review status: 0 of 7 files reviewed at latest revision, 3 unresolved discussions, all commit checks successful.

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cache/cache.go, line 22 at r2 (raw file):

Previously, pboothe (Peter Boothe) wrote…

"stale" might be better than "past". It doesn't contain the inodes from the last round of updates, it contains the inodes from the last round that did not get updated this round.

It initially contains all existing connections, as of last cycle. Connections are removed as they are replaced in the new cycle.
Changed name and added comments that hopefully make this clearer.

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cache/cache.go, line 31 at r2 (raw file):

Previously, pboothe (Peter Boothe) wrote…

...and returns the evicted value from the cache.

Done.

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inetdiag/inetdiag_test.go, line 155 at r2 (raw file):

Previously, pboothe (Peter Boothe) wrote…

I can't tell the difference between the good input data and the bad input data. Is that okay? Maybe. But I thought I should let you know.

Improved comments.

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Comments from Reviewable