Reading a C char array as a Go string

[tamilmani1989]

Hi,

My ebpf program gets process name which is retrieved as char array and i use bpf2go to generate types in golang. The golang type converting it as int8[16] and how would i convert that to string in golang?

struct verdict
{
	struct iptuple flow;
	__u32 pid;
	char comm[TASK_COMM_LEN];
	int status;
};
bpf_get_current_comm(v.comm, sizeof(v.comm));

Generated type in Go code:

type bpfVerdict struct {
	Flow   bpfIptuple
	Pid    uint32
	Comm   [16]int8
	Status int32
}

[mmat11]

You could define your struct in C code as:

struct verdict {
    ..
    __u8 comm[TASK_COMM_LEN];
    ..
};

which will generate Comm [16]uint8.

Edit: as Lorenz pointed out below, this field will likely contain a nul-terminated C string sent by the kernel, which can be parsed using https://pkg.go.dev/golang.org/x/sys/unix#ByteSliceToString. See https://go.dev/play/p/16gaV3H2yM-.

[lmb]

You'll probably want to use https://pkg.go.dev/golang.org/x/sys/unix#ByteSliceToString to deal with \x00.

[lmb]

Some more background on why char turns into int8: https://stackoverflow.com/a/2054941 Seems like you could also try -funsigned-char but then who knows what implications that has.

[tamilmani1989]

Thank you guys! It worked :)