Zhibin Li [Wed, 18 Jul 2018 10:00:58 +0000 (18:00 +0800)]
tests: check decoding of successful quotactl
* tests/quotactl-success.c: New file.
* tests/quotactl-success-v.c: Likewise.
* tests/quotactl-xfs-success.c: Likewise.
* tests/quotactl-xfs-success-v.c: Likewise.
* tests/quotactl-success.test: New test.
* tests/quotactl-success-v.test: Likewise.
* tests/quotactl-xfs-success.test: Likewise.
* tests/quotactl-xfs-success-v.test: Likewise.
* tests/.gitignore: Add quotactl-success, quotactl-success-v,
quotactl-xfs-success and quotactl-xfs-success-v.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add four new tests listed above.
* tests/quotactl.h: [INJECT_RETVAL] (check_quota): Use errstr instead of
sprintrc; check that returned value is equivalent to the injected one;
append "(INJECTED)" string to errstr.
* tests/quotactl.c: Changed condition rc != 0 to rc < 0 in callback
functions and value of opaque pointer addr_cb_arg in order to check
successful injection.
* tests/quotactl-xfs.c: Likewise.
net: enhance decoding of getsockopt(PACKET_STATISTICS)
* net.c (print_tpacket_stats): Change decoder to match the kernel
behaviour: getsockopt syscall accepts any non-negative *optlen and
writes either MIN(sizeof(struct tpacket_stats), *optlen) or
MIN(sizeof(struct tpacket_stats_v3), *optlen) bytes of data.
* net.c: Remove checks for SO_PEERCRED, SO_ATTACH_FILTER, and
SO_ATTACH_REUSEPORT_CBPF macros as they are defined unconditionally
since commit v4.23~199.
* net.c (print_ucred): Rename to print_get_ucred, change decoder
to match the kernel behaviour: getsockopt syscall accepts any
non-negative *optlen and writes MIN(sizeof(struct ucred), *optlen)
bytes of data.
(print_getsockopt): Replace print_ucred with print_get_ucred.
* tests/so_percred.c: Include <string.h>.
(main): Update expected output.
* net.c (print_get_linger): Change decoder to match the kernel
behaviour: getsockopt syscall accepts any non-negative *optlen
and writes MIN(sizeof(struct linger), *optlen) bytes of data.
(print_set_linger): Move after definition of SYS_FUNC(getsockopt).
* tests/so_linger.c: Include <stddef.h> and <string.h>.
(main): Update expected output.
* net.c (print_getsockopt): Apply (ulen < 0 || rlen < 0) check for all
cases. As the kernel neither accepts nor returns a negative length
in case of successful getsockopt syscall invocation, these negative
values must have been forged by userspace.
Workaround additional incompatibility between <sys/stat.h> and
<asm/stat.h> introduced by glibc-2.27.9000-566-gfd70af4.
* tests/xstatx.c (statx, statx_timestamp): Redefine before the inclusion
of <sys/stat.h> to avoid conflicts between definitions provided by the
linux kernel headers and the GNU libc.
Zhibin Li [Thu, 12 Jul 2018 09:32:12 +0000 (17:32 +0800)]
tests: use check_quota for invalid quotactl commands
Use check_quota function for invalid commands instead of manual quotactl
syscall invocations. In this way successful injection can also be checked
for these commands in the next commit.
* tests/quotactl.c (main): Add invalid_cmd_str and invalid_id_str local
variables, remove unused variable rc, use check_quota instead of manual
quotactl syscall invocations.
* tests/quotaclt.c (main): Add invalid_cmd_str variable, remove unused
variable rc, use check_quota instead of manual quotactl syscall invocations.
Zhibin Li [Thu, 12 Jul 2018 09:32:11 +0000 (17:32 +0800)]
tests: enhance test coverage of quotactl syscall parser
* tests/quotactl.c (print_dqfmt): New function.
(main): Use print_dqfmt to print flags of quota format, improve existing
tests and add more tests for Q_GETFMT.
* tests/quotactl-xfs.c: Improve existing tests and add more tests for
Q_XGETQSTAT and Q_XGETQSTATV.
Zhibin Li [Thu, 12 Jul 2018 06:49:42 +0000 (14:49 +0800)]
tests: extend coverage for other fcntl flags
* tests/fcntl-common.c: Include <assert.h>.
(struct fcntl_cmd_check): New structure.
(print_retval_flags, test_other_set_cmd, test_other_get_cmd,
print_flags_getfd, print_flags_getsig, print_flags_getlease,
test_fcntl_others): New functions.
(main): Use test_fcntl_others.
* xlat/bpf_attach_type.in (BPF_CGROUP_UDP4_SENDMSG,
BPF_CGROUP_UDP6_SENDMSG): New constant, introduced by Linux commit
v4.18-rc1~114^2~9^2~20^2~4.
(BPF_LIRC_MODE2): New constant, introduced by Linux commit
v4.18-rc1~114^2~9^2~15^2~1.
* xlat/bpf_commands.in (BPF_BTF_LOAD): New constant, introduced by Linux
commit v4.18-rc1~114^2~417^2~1^2~5.
(BPF_BTF_GET_FD_BY_ID): New constant, introduced by Linux commit
v4.18-rc1~114^2~223^2~21^2~4.
(BPF_TASK_FD_QUERY): New constant, introduced by Linux commit
v4.18-rc1~114^2~148^2~1^2~5.
* xlat/bpf_map_types.in (BPF_MAP_TYPE_XSKMAP): New constant, introduced
by Linux commit v4.18-rc1~114^2~304^2~4^2~8.
(BPF_MAP_TYPE_SOCKHASH): New constant, introduced by Linux commit
v4.18-rc1~114^2~223^2~5^2~2.
* xlat/bpf_prog_types.in (BPF_PROG_TYPE_LWT_SEG6LOCAL): New constant,
introduced by Linux commit v4.18-rc1~114^2~148^2~2^2~1.
(BPF_PROG_TYPE_LIRC_MODE2): New constant, introduced by Linux commit
v4.18-rc1~114^2~9^2~15^2~1.
* tests/bpf.c: Update expected output.
Wire up io_pgetevents and rseq on hppa, microblaze, mips, powerpc, and s390
* linux/hppa/syscallent.h ([350]): Wire up io_pgetevents syscall
introduced by Linux commit v4.18-rc3~7^2~2.
* linux/microblaze/syscallent.h ([399], [400]): Wire up io_pgetevents
and rseq syscalls introduced by Linux commit v4.18-rc3~33^2~2.
* linux/mips/syscallent-n32.h ([6331], [6332]): Wire up rseq and
io_pgetevents syscalls introduced by Linux commits v4.18-rc2~11^2~2
and v4.18-rc2~11^2, respectively.
* linux/mips/syscallent-n64.h ([5327], [5328]): Likewise.
* linux/mips/syscallent-o32.h ([4367], [4368]): Likewise.
* linux/powerpc/syscallent.h ([388]): Wire up io_pgetevents syscall
introduced by Linux commit v4.18-rc3~14^2~2.
* linux/powerpc64/syscallent.h ([388]): Likewise.
* linux/s390/syscallent.h ([382], [383]): Wire up io_pgetevents
and rseq syscalls introduced by Linux commits v4.18-rc4~18^2~1
and v4.18-rc4~18^2, respectively.
* linux/s390x/syscallent.h([382], [383]): Likewise.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
* maint/gen-tag-message.sh: Align the wording of the changes section
header with the one used in NEWS, add a reference to CREDITS in
"Contributors" section.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
* filter_qualify.c (qualify_kvm): Call error_msg_and_die instead of
error_msg in case of invalid -e kvm= argument.
* tests/options-syntax.test: Check it.
* tests/ioctl_kvm_run_common.c: Rename from ioctl_kvm_run.c.
(run_kvm): Parametrize printing of KVM_RUN ioctl with print_KVM_RUN
invocation.
(main): Invoke optional KVM_NO_CPUID_CALLBACK macro when the old kernel
behavior is detected.
* tests/Makefile.am (EXTRA_DIST): Add ioctl_kvm_run_common.c.
* tests/ioctl_kvm_run.c: New file, a wrapper around
ioctl_kvm_run_common.c.
* ioctl_kvm_run_auxstr_vcpu.c: Likewise.
* tests/gen_tests.in (ioctl_kvm_run_auxstr_vcpu): New test.
* tests/pure_executables.list: Add ioctl_kvm_run_auxstr_vcpu.
* tests/.gitignore: Likewise.
Signed-off-by: Masatake YAMATO <yamato@redhat.com> Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
kvm: attach the exit reason of vcpu as auxstr to KVM_RUN output
In KVM, a virtual machine implementation like Qemu can access a vcpu
via ioctl. KVM_RUN is an ioctl command to enter vcpu. The command
returns control for various reasons: needs of device emulation or
consuming time slices are the typical ones. The vmi takes a different
action for the reason.
We, strace users, want to know the reason to understand kvm. This
change prints the reason as auxstr if "-e kvm=vcpu" option is given,
and if strace runs on Linux 4.16.0 or higher, which includes commit e46b469278a59781f9b25ff608af84892963821b, "kvm: embed vcpu id to dentry
of vcpu anon inode."
The way to get the reason is a bit complicated because the ioctl does
not return it to the userspace directly. Instead, the vmi and kvm
communicate via an area of the process virtual memory where the fd of
vcpu is mmap'ed. strace must peek the area to know the reason.
The change does three things: (1) recording the area for the given vcpu
when the target calls VCPU_CREATE to vcpu_info_list per tcb data field,
(2) verifying the data recorded in vcpu_info_list before doing (3), and
(3) decoding the exit reason field of the area.
The change is complicated because there is a case that strace
does not have a chance to do (1) if -p option is used.
In this case, vcpu_info data created in the step (2).
The area has more fields than "exit reason",
dumping them may be implemented in the future.
* defs.h (struct tcb) [HAVE_LINUX_KVM_H]: Add vcpu_info_list field.
[HAVE_LINUX_KVM_H]: (kvm_run_structure_decoder_init,
kvm_vcpu_info_free): New declarations.
* strace.c (usage): Add "kvm" as a new expression for -e option.
(droptcb): Call kvm_vcpu_info_free.
* filter_qualify.c (qualify_kvm): New function calling
kvm_run_structure_decoder_init to enable for attaching the exit
reason to auxstr.
(qual_options): Add "kvm" as an entry.
* xlat/kvm_exit_reason.in: New file.
* kvm.c: Include xmalloc.h and mmap_cache.h.
(dump_kvm_run_structure): New static variable.
(kvm_run_structure_decoder_init): New function.
(vcpu_info): New struct definition representing the 3-tuple: vcpu file
descriptor, id of the vcpu, and mmap'ed entry.
(vcpu_find, vcpu_alloc, vcpu_register, vcpu_getinfo,
kvm_vcpu_info_free): New functions to access tcb's vcpu_info_list
field and vcpu_info data type.
(is_map_for_file, map_len): New helper functions.
(kvm_ioclt_run_attach_auxstr, kvm_ioctl_decode_run): New functions
decoding vcpu exit reason and attaching the decoded data to auxstr
field of tcb.
(kvm_ioctl_create_vcpu): Call vcpu_register to make an entry mapping
a file descriptor and the vcpu id associated with the fd.
(kvm_ioctl): Call kvm_ioctl_decode_run.
Signed-off-by: Masatake YAMATO <yamato@redhat.com> Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
* mmap_cache.c (mmap_cache_search_custom): New function.
* mmap_cache.h (mmap_cache_search_fn): New type.
(mmap_cache_search_custom): New function prototype.
Pierre Marsais [Thu, 28 Jun 2018 02:37:44 +0000 (03:37 +0100)]
tests: check decoding of kvm ioctls related to struct kvm_cpuid2
* tests/ioctl_kvm_run.c [!HAVE_STRUCT_KVM_CPUID2]: Skip the test.
(KVM_MAX_CPUID_ENTRIES): New macro.
(print_cpuid_ioctl): New function.
(main): Add tests for cpuid related ioctl.
Signed-off-by: Pierre Marsais <pierre.marsais@lse.epita.fr>
Reduce false positives by wrapping network-related operations into a loop.
* ci/install-dependencies.sh (retry_if_failed): New function.
Use it to invoke apt-get update, apt-get install, git clone,
add-apt-repository, and pip install.
Dmitry V. Levin [Mon, 18 Jun 2018 22:59:38 +0000 (22:59 +0000)]
Fix build on systems where libc relies on <linux/signal.h>
Commit v4.23~10 has broken the build with Android's libc because it
relies on the UAPI headers (such as <linux/signal.h>) to define various
types, rather than copying them into the libc headers (such as <signal.h>)
like most other Linux C libraries.
* linux/linux/signal.h: Rename to linux/signal.h.in.
* Makefile.am (strace_SOURCES): Remove linux/linux/signal.h.
(EXTRA_DIST): Add linux/signal.h.in.
(DISTCLEANFILES): Add linux/linux/signal.h.
* configure.ac (AC_CACHE_CHECK): Check whether <linux/signal.h>
can be used along with <signal.h>, install linux/linux/signal.h
workaround if they cannot be used together.
* xlat/aio_cmds.in: New file.
* aio.c (tprint_lio_opcode): Change array of structs "cmds" to array of
enums "subs", use printxval_indexn_ex for printing cmd, return sub type
using subs array.
* xlat/sock_tcp_options.in (TCP_ZEROCOPY_RECEIVE): New constant,
introduced by Linux commit v4.18-rc1~114^2~351^2~1.
(TCP_INQ): New constant, introduced by Linux commit v4.18-rc1~114^2~330.
* print_aio_sigset.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* aio.c (print_io_getevents): Rename from SYS_FUNC(io_getevents), add
has_usig flag, print user sigset on exiting if has_usig is set to true.
(SYS_FUNC(io_getevents), SYS_FUNC(io_pgetevents)): New functions,
wrappers for print_io_getevents.
* linux/32/syscallent.h ([292]): Wire up io_pgetevents.
* linux/64/syscallent.h ([292]): Likewise.
* linux/i386/syscallent.h ([385]): Likewise.
* linux/x32/syscallent.h ([333]): Likewise.
* linux/x86_64/syscallent.h ([333]): Likewise.
* NEWS: Mention this improvement.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
Dmitry V. Levin [Tue, 12 Jun 2018 12:27:22 +0000 (12:27 +0000)]
travis: re-enable testing with the latest mainline kernel headers
As <linux/signal.h> is out of the game now, the Linux commit v4.17-rc3-7-g7a074e9 should not cause harm anymore, so let's enable
testing with the latest mainline kernel headers again.
* .travis.yml (matrix): Do not specify KBRANCH for KHEADERS=torvalds/linux.
Add support for personality designation in regex qualifications
* basic_filters.c (qualify_syscall_regex): Copy syscall name
to a temporary buffer, append the personality designation to it,
and check it against regular expression if the syscall name
hasn't been matched already.
Add support for personality designation in syscall qualifications
* syscall.c (personality_designators): New array.
* defs.h (personality_designators): New declaration.
* basic_filters.c (qualify_syscall_separate_personality,
qualify_syscall_number_personality): New functions.
(qualify_syscall_number): Use qualify_syscall_separate_personality for
checking for a personality specification, call
qualify_syscall_number_personality for setting number set for specific
personality.
(qualify_syscall_name_personality): New function.
(qualify_syscall_name): Use qualify_syscall_separate_personality for
checking for a personality specification, call
qualify_syscall_name_personality for setting number set for specific
personality.
* strace.1.in (.SS Filtering): Document it.
* NEWS: Mention it.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org> Closes: https://github.com/strace/strace/issues/35
Implement injection of syscalls with no side effects as an alternative to -1
* defs.h (INJECT_F_SYSCALL, INJECT_ACTION_FLAGS, TCB_TAMPERED_NO_FAIL,
syscall_tampered_nofail): New macros.
(inject_data): Add scno field.
* filter_qualify.c (struct inject_personality_data): New type.
(parse_inject_token): Add "pdata" argument, parse "syscall=" option.
(parse_inject_expression): Add "pdata" argument, forward it to
parse_inject_token.
(qualify_inject_common) <pdata>: New variable array, pass it to
parse_inject_expression, copy it into inject_vec.
* syscall.c (tamper_with_syscall_entering): Inject the specified syscall
if INJECT_F_SYSCALL is set.
(tamper_with_syscall_exiting): Update the check for a failed syscall
injection.
(get_syscall_result): Update get_error invocation.
* strace.1.in: Document new syscall injection expression.
* NEWS: Mention it.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org> Closes: https://github.com/strace/strace/issues/26
linux: set error flags in arch_set_error on POWER and Alpha
* alpha/set_error.c (arch_set_error): Set alpha_r3 to 1, update tracee's
REG_A3.
* powerpc/set_error.c (arch_set_error): Set bit 28 in CCR register,
update tracee's PT_CCR.
Fixes: v4.15~126 "Implement arch specific methods of changing syscall number and error code"
tests: add fallback_func argument to TEST_NESTED_NLATTR_OBJECT_EX_
* tests/test_nlattr.h (TEST_NESTED_NLATTR_OBJECT_EX_): Add fallback_func
argument, call it instead of print_quoted_hex.
(TEST_NESTED_NLATTR_OBJECT_EX, TEST_NESTED_NLATTR_OBJECT): Specify
print_quoted_hex as a fallback_func.
* tests/nlattr_ifla_af_spec.c: Specify print_quoted_hex as
a fallback_func in TEST_NESTED_NLATTR_OBJECT_EX_ calls.
tests/test_nlattr.h: add ability to provide additional nlattr payload
* tests/test_nlattr.h (print_nlattr): Add add_data argument, print
opening square bracket if add_data is set to true.
(TEST_NLATTR_EX_): Rename from TEST_NLATTR_, add nla_total_len_
argument, use it for msg_len calculation, print square brackets
if nla_total_len_ is greater than nla_data_len_.
(TEST_NLATTR_): New macro, a wrapper for TEST_NLATTR_EX_.
* rtnl_link.c (decode_ifla_bridge_id): Provide struct definition for
the id variable.
[!HAVE_STRUCT_IFLA_BRIDGE_ID] (decode_ifla_bridge_id): Decode struct
ifla_bridge_id.
rtnl_link: fix incorrect variable names in ARRAY_SIZE arguments
* rtnl_link.c (decode_nla_linkinfo_data_bridge): Change
rtnl_ifla_info_data_bridge_attrs to ifla_info_data_bridge_nla_decoders
in ARRAY_SIZE call.
(decode_nla_linkinfo_data_tun): Change rtnl_ifla_info_data_tun_attrs
to ifla_info_data_tun_nla_decoders in ARRAY_SIZE call.
Fixes: v4.22-328-g1e6d5a8 "rtnl_link: implement IFLA_INFO_DATA for bridges" Fixes: v4.22-329-g4eab3a4 "rtnl_link: implement IFLA_INFO_DATA for tun devices"
Dmitry V. Levin [Thu, 7 Jun 2018 14:01:24 +0000 (14:01 +0000)]
configure.ac: fix the check for struct tc_sizespec on old kernel headers
* configure.ac (AC_CHECK_TYPES): Include <linux/types.h> before
<linux/pkt_sched.h> to check for struct tc_sizespec on linux kernel
headers without v2.6.29-rc4~77^2~26 fix.
tests: add TEST_NESTED_NLATTR_ARRAY_EX to test_nlattr.h
An ability to specify custom depth is going to be needed later to check
IFLA_AF_SPEC decoding.
* configure.ac (AC_CHECK_DECLS): Check for TCA_STAB_DATA in
<linux/pkt_sched.h>.
* tests/test_nlattr.h (TEST_NESTED_NLATTR_ARRAY_EX): Rename from
TEST_NESTED_NLATTR_ARRAY, add depth_ argument, perform padding and
output accordingly.
(TEST_NESTED_NLATTR_ARRAY): New macro, a thin wrapper around
TEST_NESTED_NLATTR_ARRAY_EX.
* tests/nlattr_tca_stab.c [!HAVE_DECL_TCA_STAB_DATA] (TCA_STAB_DATA):
New enumeration declaration.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
tests: pass index to print_elem_ callback in TEST_NLATTR_NESTED_ARRAY
* tests/test_nlattr.h (TEST_NLATTR_NESTED_ARRAY): Pass array index
to the print_elem_ callback.
* tests/nlattr_tca_stab.c (print_uint16): Add index argument.
tests: move common ifinfomsg boilerplate into a separate header
* configure.ac (AC_CHECK_DECLS): Check for IFLA_PORT_SELF, IFLA_PROTINFO, and
IFLA_XDP in <linux/rtnetlink.h>.
* tests/nlattr_ifla.h: New file.
* tests/Makefile.am (EXTRA_DIST): Add it.
* tests/nlattr_ifla_brport.c [!HAVE_DECL_IFLA_PROTINFO] (IFLA_PROTINFO):
New declaration.
(hdrlen, init_ifinfomsg, print_ifinfomsg): Remove.
(IFLA_ATTR): Define to IFLA_PROTINFO.
Include nlattr_ifla.h.
* tests/nlattr_ifla_port.c [!HAVE_DECL_IFLA_PORT_SELF] (IFLA_PORT_SELF):
New declaration.
(hdrlen, init_ifinfomsg, print_ifinfomsg): Remove.
(IFLA_ATTR): Define to IFLA_PORT_SELF.
Include nlattr_ifla.h.
* tests/nlattr_ifla_xdp.c
* tests/nlattr_ifla_xdp.c [!HAVE_DECL_IFLA_XDP] (IFLA_XDP): New
declaration.
(hdrlen, init_ifinfomsg, print_ifinfomsg): Remove.
(IFLA_ATTR): Define to IFLA_XDP.
Include nlattr_ifla.h.
rtnl_link: implement IFLA_INFO_DATA for tun devices
* xlat/rtnl_ifla_info_data_tun_attrs.in: New file.
* xlat/tun_device_types.in: Likewise.
* rtnl_link.c: Include xlat/rtnl_ifla_info_data_tun_attrs.h and
xlat/tun_device_types.h.
(decode_nla_tun_type, decode_nla_linkinfo_data_tun): New functions.
(ifla_info_data_tun_nla_decoders): New decoder dispatcher table.
(decode_nla_linkinfo_data): Use decode_nla_linkinfo_data_tun if kind
is
"tun".
* xlat/rtnl_ifla_info_data_bridge_attrs.in: New file.
* rtnl_link.c: Include xlat/rtnl_ifla_info_data_bridge_attrs.h.
(ifla_info_data_bridge_nla_decoders): New decoder dispatcher table.
(decode_nla_linkinfo_data_bridge, decode_nla_linkinfo_data): New
functions.
(ifla_linkinfo_nla_decoders) <IFLA_INFO_DATA>: Use
decode_nla_linkinfo_data as a decoder.
* rtnl_link.c (decode_nla_linkinfo_xstats_can,
decode_nla_linkinfo_xstats): New function.
(ifla_linkinfo_nla_decoders) <IFLA_INFO_XSTATS>: Use
decode_nla_linkinfo_xstats as a decoder.
Dispatch for IFLA_INFO_* attributes should be performed based on the
string provided in a IFLA_INFO_KIND attribute.
* nlattr.h (struct ifla_linkinfo_ctx): New type definition.
* rtnl_link.c (decode_nla_linkinfo_kind): New function.
(ifla_linkinfo_nla_decoders) <IFLA_INFO_KIND>: Use
decode_nla_linkinfo_kind as decoder.
(decode_ifla_linkinfo): Add struct ifla_linkinfo_ctx context, pass it to
the decode_nlattr call as opaque data.
nlattr: add size check to decode_nla_xval and decode_nla_flags
If the field size is known, do not print as valid numbers those
attributes that are too short, and ignore extra data.
This change puts xval/flags printing in line with the reset of attribute
decoders.
* nlattr.h (struct decode_nla_xlat_opts): Add size field.
* nlattr.c (decode_nla_xval, decode_nla_flags): Check that len is at
least opts->size, limit len to opts->size.
(decode_nla_ip_proto): Specify size of 1.
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
nlattr: add value processing support for xlat/flags nlattr decoders
Needed for upcoming decoder of ethernet proto which is stored in the
host order and has to be converted to the network order before printing
as an xval constant. This change also adds ability to provide
prefix/suffix in order to enclose the printed value in something that
describes the performed conversion.
nlattr: add ability to pass nla_type to decoder in decode_nlattr
As of now, it's impossible to introduce a dispatching nlattr decoder
that performs actions based on the type of the message, so let's use
a combination of zero decoder list size and non-zero decoder pointer
for this.
This is going to be used later in IFLA_AF_SPEC decoding.
* nlattr.c (decode_nlattr_with_data): Handle zero size and non-NULL
decoders in a special way.
(decode_nlattr): Add an error message about ignoring of opaque_data
argument when zero size and non-NULL decoders are provided.
* nlattr.h (decode_nlattr): Add a comment about the new special case.
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