On Mon, Jun 19, 2017 at 12:45:51PM +0900, Masatake YAMATO wrote:
> GENERIC is a protocol stacked on Netlink protocol. Via GENERIC
> protocol, a process can communicate with a kernel subsystem.
>
> An integer named "family" is assigned to each subsystem that can be
> communicated via GENERIC protocol. A process sets the integer to the
> type field of Netlink packet.
>
> A subsystem registers its name to the kernel at run-time, and gets an
> integer for family. So even strace can know the integer that the
> target process uses in the communication, a user of strace cannot know
> the subsystem which the target process communicates with.
>
> This change decodes the integer for family which is stored to the
> type field by accessing kernel at run-time.
>
> Example session:
>
> $ ./strace -yy -e 'sendto' ip tcp_metrics > /dev/null
> sendto(4<NETLINK:[GENERIC:7939]>, {{len=20, type=tcp_metrics, ...
> +++ exited with 0 +++
>
> type= that specifies a family in Netlink GENERIC protocol
> is decoded well.
>
> * netlink.c (nlmsg_types): Remove const modifiers to allow to
> install a xlat table for decoding the field made at run-time.
> Add an element for NETLINK_GENERIC.
> (decode_nlmsg_type): Install the xlat table to the NETLINK_GENERIC
> element of nlmsg_types.
I've reworded this commit message, hope it's OK.
> Changes in v4:
>
> * Update this log to clear the relationship between an integer
> for "family" and "type" field.
>
> Signed-off-by: Masatake YAMATO <yam...@redhat.com>
> ---
> netlink.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/netlink.c b/netlink.c
> index 4bef949..ff837f4 100644
> --- a/netlink.c
> +++ b/netlink.c
> @@ -109,6 +109,15 @@ decode_nlmsg_type_default(const struct xlat *const xlat,
> }
>
> static void
> +decode_nlmsg_type_generic(const struct xlat *const xlat,
> + const uint16_t type,
> + const char *const dflt)
> +{
> + const struct xlat *const my_xlat = genl_families_xlat();
> + printxval(my_xlat, type, dflt);
I've replaced these two lines with a single line:
printxval(genl_families_xlat(), type, dflt);
> +}
> +
> +static void
> decode_nlmsg_type_netfilter(const struct xlat *const xlat,
> const uint16_t type,
> const char *const dflt)
> @@ -146,6 +155,11 @@ static const struct {
> const char *const dflt;
> } nlmsg_types[] = {
> [NETLINK_AUDIT] = { NULL, nl_audit_types, "AUDIT_???" },
> + [NETLINK_GENERIC] = {
> + decode_nlmsg_type_generic,
> + NULL,
> + "GENERIC_FAMILY_???"
> + },
> [NETLINK_NETFILTER] = {
> decode_nlmsg_type_netfilter,
> nl_netfilter_subsys_ids,
Applied, thanks!
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