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cgolmnl

Go wrapper of libmnl using cgo, under heavy development

sample

see examples

installation

Need running mktypes.sh before build.

requires

links

struct

mnl_nlmsg_batch and mnl_socket are opaque as NlmsgBatch and Socket (cgo say [0]byte). Nlattr is same as C struct but Nlmsg seems a little bit strange. It has buf and real Nlmsghdr.

errno

I currently use an incredibly childish C function in set_errno.c

void SetErrno(int n) { errno = n; }

I can not find the way of tossing up Go callback error, in other words set C's errno from Go. I am not good at English, let me show why I need to do in the code snippets below:

  • C library header (lib.h)
    typedef int cbf_t(void *data);
    extern int c_func(cbf_t cbfunc, void *data);
  • wrapper header
    #include "lib.h"
    #include "_cgo_export.h"
    extern int wrap(void *data);
  • C wrapper source
    #include "cblib.h"
    int wrap(void *data)
    {
        return c_func((cbf_t)CallFromC, data);
    }
  • Go
    /*
    #include "cbwrap.h"
    */
    import "C"
    import "unsafe"

    type Cb_t func(interface {}) (int, error)

    func Doit(cbfunc Cb_t, data interface{}) (int, error) {
        // multiplexing
        pseudo_data := [2]unsafe.Pointer{unsafe.Pointer(&cbfunc), unsafe.Pointer(&data)}
        return C.wrap(unsafe.Pointer(&pseudo_data))
    }

    //export CallFromC
    func CallFromC(pseudo_data interface) C.int {
        // demultiplexing
        args := *(*[2]unsafe.Porinter)(pseudo_data)
        cbfunc := *(*Cb_t)(args[0])
        real_data := *(*interface{})(args[1])
        ret, err := cbfunc(real_data)
	// set C errno here
    }

    func cb(data interface{}) (int, error) {
        i := data.(int)
        if i < 0:
	    return -1, syscall.Errno(-i)
        else:
	    return i, syscall.Errno(0)
    }

    func main() {
        Doit(cb, 7)
    }

call chain will be: Go main() -> Go Doit() -> C wrap() -> C c_func() -> Go CallFromC() -> Go cb()

I need to know the way of tossing last Go cb() error up to Go Doit() or C c_func().

comparison

original cgolmnl remarks
mnl_attr_get_type Nlattr.GetType
mnl_attr_get_len Nlattr.GetLen
mnl_attr_get_payload_len Nlattr.GetPayloadLen
mnl_attr_get_payload Nlattr.GetPayload
(add) Nlattr.GetPayloadBytes returns []byte
mnl_attr_ok Nlattr.Ok
mnl_attr_next Nlattr.Next
mnl_attr_type_valid Nlattr.TypeValid returns ret, error
mnl_attr_validate Nlattr.Validate returns ret, errno
mnl_attr_validate2 Nlattr.Validate2 returns ret, errno
mnl_attr_parse Nlattr.Parse returns ret, errno
mnl_attr_parse_nested Nlattr.ParseNested returns ret, errno
mnl_attr_parse_payload Nlattr.ParsePayload returns ret, errno
mnl_attr_get_u8 Nlattr.GetU8
mnl_attr_get_u16 Nlattr.GetU16
mnl_attr_get_u32 Nlattr.GetU32
mnl_attr_get_u64 Nlattr.GetU64
mnl_attr_get_str Nlattr.GetStr
mnl_attr_put Nlattr.Put
(add) Nlattr.PutPtr
(add) Nlattr.PutBytes
mnl_attr_put_u8 Nlattr.PutU8
mnl_attr_put_u16 Nlattr.PutU16
mnl_attr_put_u32 Nlattr.PutU32
mnl_attr_put_u64 Nlattr.PutU64
mnl_attr_put_str Nlattr.Putstr
mnl_attr_put_strz Nlattr.Putstrz
mnl_attr_nest_start Nlattr.NestStart
mnl_attr_put_check Nlattr.PutCheck
mnl_attr_put_u8_check Nlattr.PutU8Check
mnl_attr_put_u16_check Nlattr.PutU16Check
mnl_attr_put_u32_check Nlattr.PutU32Check
mnl_attr_put_u64_check Nlattr.PutU64Check
mnl_attr_put_str_check Nlattr.PutStrCheck
mnl_attr_put_strz_check Nlattr.PutStrzCheck
mnl_attr_nest_start_check Nlattr.nestStartCheck
mnl_attr_nest_end Nlattr.nestEnd
mnl_attr_nest_cancel Nlattr.nestCancel
------------------------------------- ----------------------------- -----------------------------
mnl_nlmsg_size NlmsgSize
mnl_nlmsg_get_payload_len Nlmsg.GetPayloadLen
mnl_nlmsg_put_header Nlmsg.PutHeader
(add) NlmsgBytes build new nlmsg from []byte
(add) NewNlmsg build new nlmsg
mnl_nlmsg_put_extra_header Nlmsg.PutExtraHeader
mnl_nlmsg_get_paylod Nlmsg.GetPayload
(add) Nlmsg.GetPayloadBytes returns []byte
mnl_nlmsg_get_payload_offset Nlmsg.GetPayloadOffset
(add) Nlmsg.GetPayloadOffsetBytes returns []byte
mnl_nlmsg_ok Nlmsg.Ok
mnl_nlmsg_next Nlmsg.Next
mnl_nlmsg_get_payload_tail Nlmsg.GetPayloadTail
mnl_nlmsg_seq_ok Nlmsg.SeqOk
mnl_nlmsg_portid_ok Nlmsg.PortidOk
mnl_nlmsg_fprintf Nlmsg.Fprint *os.File, not descriptor
mnl_nlmsg_batch_start NewNlmsgBatch
mnl_nlmsg_batch_stop NlmsgBatch.Stop
mnl_nlmsg_batch_next NlmsgBatch.Next
mnl_nlmsg_batch_reset NlmsgBatch.Reset
mnl_nlmsg_batch_size NlmsgBatch.Size
mnl_nlmsg_batch_head NlmsgBatch.Head
(add) NlmsgBatch.HeadBytes returns []byte
mnl_nlmsg_batch_current NlmsgBatch.Current
mnl_nlmsg_batch_is_empty NlmsgBatch.IsEmpty
------------------------------------- ----------------------------- -----------------------------
mnl_cb_run CbRun
mnl_cb_run2 CbRun2 changed signature
------------------------------------- ----------------------------- -----------------------------
mnl_socket_get_fd Socket.GgetFd
mnl_socket_get_portid Socket.GetPortid
mnl_socket_open NewSocket
mnl_socket_open2 NewSocket2
mnl_socket_fdopen NewSocketFd
mnl_socket_bind Socket.Bind
mnl_socket_sendto Socket.Sendto
(add) Socket.SendNlmsg
mnl_socket_recvfrom Socket.Recvfrom
mnl_socket_close Socket.Close
mnl_socket_setsockopt Socket.Setsockopt
mnl_socket_getsockopt Socket.Getsockopt