Hi Michael thanks again for the answer. Also I found the answer by myself.
Apparently, it was not a problem between Read() and Write(). The issue is that https://github.com/songgao/water <https://www.google.com/url?q=https%3A%2F%2Fgithub.com%2Fsonggao%2Fwater&sa=D&sntz=1&usg=AFQjCNExGUanzVUJCzlw7vattjCbxai86g> is not working as declared. The Read() implementation is returning an amount of bytes which is always 42 or 46. Which is correct, until you don't try to truncate the buffer to this size. To be precise, refering to the example in its page: for { frame.Resize(1500) n, err := ifce.Read([]byte(frame)) if err != nil { log.Fatal(err) } *frame = frame[:n]* log.Printf("Dst: %s\n", frame.Destination()) log.Printf("Src: %s\n", frame.Source()) log.Printf("Ethertype: % x\n", frame.Ethertype()) log.Printf("Payload: % x\n", frame.Payload()) } when you truncate *frame = frame[:n] *you are doing a mess. This is because the 42 or 46 is not comprensive of the whole amount of data you've read. If I stop truncating the buffer like that, I get by example: V-SWITCH> 2017/06/17 20:44:10 *Size: 42* > V-SWITCH> 2017/06/17 20:44:11 Src: 8e:f0:68:17:27:cb , Broadcast :false > V-SWITCH> 2017/06/17 20:44:11 Dst: ff:ff:ff:ff:ff:ff , Broadcast :true > V-SWITCH> 2017/06/17 20:44:11 Ethertype: 08 06 > V-SWITCH> 2017/06/17 20:44:11 Payload: 00 01 08 00 06 04 00 01 8e f0 68 17 > 27 cb 0a 00 09 02 00 00 00 00 00 00 0a 00 09 01 4d 2d 53 45 41 52 43 48 20 > 2a 20 48 54 54 50 2f 31 2e 31 0d 0a 48 4f 53 54 3a 20 32 33 39 2e 32 35 35 > 2e 32 35 35 2e 32 35 30 3a 31 39 30 30 0d 0a 4d 41 4e 3a 20 22 73 73 64 70 > 3a 64 69 73 63 6f 76 65 72 22 0d 0a 4d 58 3a 20 31 0d 0a 53 54 3a 20 75 72 > 6e 3a 64 69 61 6c 2d 6d 75 6c 74 69 73 63 72 65 65 6e 2d 6f 72 67 3a 73 65 > 72 76 69 63 65 3a 64 69 61 6c 3a 31 0d 0a 55 53 45 52 2d 41 47 45 4e 54 3a > 20 47 6f 6f 67 6c 65 20 43 68 72 6f 6d 65 2f 35 39 2e 30 2e 33 30 37 31 2e > 31 30 34 20 4c 69 6e 75 78* 0d 0a 0d 0a* 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 if you keep the whole mtu and you print n, you see that this lenght is NOT the lenght of the whole frame. The Payload alone is much bigger than 42 , and it ends with 0d 0a, twice (because of the protocol). If you truncate the buffer to 42 or 46, you get an unusable frame. Unusable means it will work with ARP/RARP, but not with other protocols. I hope this may prevent other people to waste their time with this library, at least to don't use as suggested. The next is how to truncate a []byte removing the exceeding zeroes, which is a completely different question. > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
