panic: runtime error: cgo argument has Go pointer to Go pointer

[rajender]

pfdump gave following error with go1.6beta2, but working fine with go1.5. Seems like new cgo rules are the reason. See https://tip.golang.org/cmd/cgo/#hdr-Passing_pointers

Starting to read packets
panic: runtime error: cgo argument has Go pointer to Go pointer

goroutine 53 [running]:
github.com/google/gopacket/pfring.(_Ring).ReadPacketDataTo(0xc821280000, 0xc82129a000, 0x10000, 0x10000, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/root/ws/src/github.com/google/gopacket/pfring/pfring.go:116 +0x210
github.com/google/gopacket/pfring.(_Ring).ReadPacketData(0xc821280000, 0xc82129a000, 0x10000, 0x10000, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/root/ws/src/github.com/google/gopacket/pfring/pfring.go:135 +0xcb
github.com/google/gopacket.(_PacketSource).NextPacket(0xc821270c60, 0x0, 0x0, 0x0, 0x0)
/root/ws/src/github.com/google/gopacket/packet.go:759 +0x76
github.com/google/gopacket.(_PacketSource).packetsToChannel(0xc821270c60)
/root/ws/src/github.com/google/gopacket/packet.go:776 +0x54
created by github.com/google/gopacket.(*PacketSource).Packets
/root/ws/src/github.com/google/gopacket/packet.go:799 +0x7f

[LrsK]

I am also seeing this with Go 1.6

[gconnell]

I'm having trouble reproducing this:

gconnell@loftyduck:~/go/src/github.com/google/gopacket/pfring$ uname -a
Linux loftyduck.dls.corp.google.com 3.13.0-77-generic #121-Ubuntu SMP Wed Jan 20 10:50:42 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
gconnell@loftyduck:~/go/src/github.com/google/gopacket/pfring$ go version
go version go1.6 linux/amd64
gconnell@loftyduck:~/go/src/github.com/google/gopacket/pfring$ git branch
* master
gconnell@loftyduck:~/go/src/github.com/google/gopacket/pfring$ git pull
Already up-to-date.
gconnell@loftyduck:~/go/src/github.com/google/gopacket/pfring$ go version
go version go1.6 linux/amd64
gconnell@loftyduck:~/go/src/github.com/google/gopacket/pfring$ go build && echo SUCCESS
SUCCESS

[LrsK]

It happens at runtime for me when using the afpacket mode and fetching the stats using tpacket.SocketStats(). It fails here for me: https://github.com/google/gopacket/blob/master/afpacket/afpacket.go#L293 but I'm able to capture packets without issues.

[LrsK]

I've been discussing this with the golang Google group, and it seems like the pointer checker is a bit overzealous in this case.

Their suggestion was to go from:

_, err := C.getsockopt(h.fd, C.SOL_PACKET, C.PACKET_STATISTICS, unsafe.Pointer(&h.socketStatsV3), &slt)

to something like:

var ssv3 SocketStatsV3
C.getsockopt(..., &ssv3, ...)
h.socketStatsV3 = ssv3

I will try this and report back.

[gconnell]

Could you try this pull request to see if it fixes your issue?

#180

[LrsK]

#180 Did fix the pfring code, I have confirmed that now. As you can see I also added a fix for the socket stats.

[LrsK]

#182 added for your consideration. It simplifies the code in PR #181

[gconnell]

182 merged, closing as I think this is now fixed.