How to send packets size with 60000？

[hel2o]

when i set pinger.Size = 60000 ,but packets is not send

[sparrc]

I believe this may have been fixed by #45, can you update to the latest commit of go-ping and try again?

[SuperQ]

I think there are still issues with the size option.

When I set p.Size = 256, tcpdump says the packet length is 394.

When I set p.Size = 321, tcpdump says the packet length is 478.

When I set p.Size = 322, tcpdump says the packet length is 482, and panics my prober.

panic: runtime error: slice bounds out of range

goroutine 39 [running]:
github.com/superq/smokeping_prober/ping.(*Pinger).processPacket(0xc000159110, 0xc0001609c0, 0x4, 0x3)
	/home/ben/go/src/github.com/superq/smokeping_prober/ping/ping.go:435 +0x6be
github.com/superq/smokeping_prober/ping.(*Pinger).run(0xc000159110)
	/home/ben/go/src/github.com/superq/smokeping_prober/ping/ping.go:321 +0x4e1
github.com/superq/smokeping_prober/ping.(*Pinger).Run(0xc000159110)
	/home/ben/go/src/github.com/superq/smokeping_prober/ping/ping.go:270 +0x2b
created by main.main
	/home/ben/go/src/github.com/superq/smokeping_prober/main.go:95 +0xf09

[sparrc]

I'm going to hazard a guess that this has something to do with the code still referencing timeSliceLength, which is used as a constant to initialize the size of the packet sent. This constant likely needs to be removed and the logic around it changed.

https://github.com/sparrc/go-ping/blob/ef3ab45e41b017889941ea5bb796dd502d2b5a1b/ping.go#L514

[SuperQ]

Yea, that bit didn't look right to me at all, but I didn't have time to poke around.

[CHTJonas]

Using the latest commit on master and with sudo tcpdump icmp running in another terminal tab:

• pinger.Size = 256 logs an ICMP echo request packet with length 264.
• pinger.Size = 321 logs an ICMP echo request packet with length 329.
• pinger.Size = 322 logs an ICMP echo request packet with length 330.
• pinger.Size = 1472 logs an ICMP echo request packet with length 1480.

ICMP packets have an 8-byte header so this all seams correct to me.

If you set a (IMHO silly) packet size pinger.Size = 60000 (or indeed anything above 1472 in most instances) then the ICMP datagram gets fragmented across multiple IP packets at the network MTU. I don't really think we can expect things to behave reliably is such circumstances so if the user sets Size > MTU then they get to keep both pieces.