prog, sys: add tcp packets descriptions #122
Conversation
| var csum IPChecksum | ||
| csum.Update(encodeArg(srcAddr, pid)) | ||
| csum.Update(encodeArg(dstAddr, pid)) | ||
| csum.Update(append([]byte{0}, encodeArg(protocol, pid)...)) |
There was a problem hiding this comment.
Why do you do append([]byte{0}, ...?
it is used to make a copy of a slice, but the slice returned by encodeArg is already not aliased with anything else.
There was a problem hiding this comment.
I want to make an array of two bytes, the first one is 0 and the second one is the protocol id (the protocol field encodes into 1 byte).
Is there a way to do this better?
There was a problem hiding this comment.
Ah, OK, I missed the {0} part.
Simple/faster way may be:
[]byte{0, byte(protocol.Value(pid))}
| } | ||
|
|
||
| func calcChecksumIPv4(arg *Arg, pid int) (*Arg, *Arg) { | ||
| csumField := findFieldByName(arg, "csum") | ||
| if csumField == nil { |
There was a problem hiding this comment.
I would move the nil check and panic into findFieldByName itself, because it is duplicated multiple times.
It is also possible to type/size checks into findFieldByName. If some of the checks are optional, then you can use 0/nil as 'don't check'.
Also embed tcp checksums into packets.
Also embed tcp checksums into packets.