Hi Duncan,
On Wed, 12 Mar 2025, Duncan Roe wrote:
On Tue, Mar 11, 2025 at 10:00:04AM +0000, G.W. Haywood wrote:
Debian 11, gcc version 10.2.1-6 here.
8<----------------------------------------------------------------------
$ gcc -g3 -gdwarf-4 -Wall -lmnl -lnetfilter_queue -o nf-queue nf-queue.c
/usr/bin/ld: /tmp/ccbLJv89.o: in function `nfq_send_verdict':
/home/ged/nf-queue.c:30: undefined reference to `nfq_nlmsg_put'
...
...
collect2: error: ld returned 1 exit status
8<----------------------------------------------------------------------
nf-queue.c has compiled fine.
Quite so, but it hasn't linked and no executable has been produced... :/
However, with the object and source file args at the beginning of the
command line, there are no linker errors and the executable is produced.
There is a problem with the shared libraries libmnl.so and
libnetfilter_queue.so. Those 2 libraries should satisfy the mnl_ and nfq_
references respectively.
Obviously I do have them installed.
On my (Slackware x86_64) system, "nm -D /usr/lib64/libmnl.so|grep -Ew T" gives:
| 0000000000003687 T mnl_attr_get_len@@LIBMNL_1.0
| 00000000000036ac T mnl_attr_get_payload@@LIBMNL_1.0
| 0000000000003698 T mnl_attr_get_payload_len@@LIBMNL_1.0
| ...
for a total of 68 lines. What do you get? (you may have to put /usr/lib instead
of /usr/lib64).
The libraries are in /usr/lib/aarch64-linux-gnu/, and yes, 68 lines output:
8<----------------------------------------------------------------------
$ nm -D /usr/lib/aarch64-linux-gnu/libmnl.so|grep -Ew T | head
0000000000002ad8 T mnl_attr_get_len@@LIBMNL_1.0
0000000000002af0 T mnl_attr_get_payload@@LIBMNL_1.0
0000000000002ae0 T mnl_attr_get_payload_len@@LIBMNL_1.0
0000000000002f20 T mnl_attr_get_str@@LIBMNL_1.0
0000000000002ac8 T mnl_attr_get_type@@LIBMNL_1.0
0000000000002ed8 T mnl_attr_get_u16@@LIBMNL_1.0
0000000000002ef0 T mnl_attr_get_u32@@LIBMNL_1.0
0000000000002f08 T mnl_attr_get_u64@@LIBMNL_1.0
0000000000002ec0 T mnl_attr_get_u8@@LIBMNL_1.0
00000000000032a0 T mnl_attr_nest_cancel@@LIBMNL_1.0
0000000000003278 T mnl_attr_nest_end@@LIBMNL_1.0
00000000000030a8 T mnl_attr_nest_start@@LIBMNL_1.0
0000000000003250 T mnl_attr_nest_start_check@@LIBMNL_1.0
0000000000002c30 T mnl_attr_next@@LIBMNL_1.0
0000000000002c00 T mnl_attr_ok@@LIBMNL_1.0
0000000000002d08 T mnl_attr_parse@@LIBMNL_1.0
0000000000002da0 T mnl_attr_parse_nested@@LIBMNL_1.0
0000000000002e40 T mnl_attr_parse_payload@@LIBMNL_1.1
0000000000002f28 T mnl_attr_put@@LIBMNL_1.0
00000000000030e0 T mnl_attr_put_check@@LIBMNL_1.0
0000000000003018 T mnl_attr_put_str@@LIBMNL_1.0
00000000000031b0 T mnl_attr_put_str_check@@LIBMNL_1.0
0000000000003060 T mnl_attr_put_strz@@LIBMNL_1.0
0000000000003200 T mnl_attr_put_strz_check@@LIBMNL_1.0
0000000000002fb8 T mnl_attr_put_u16@@LIBMNL_1.0
0000000000003150 T mnl_attr_put_u16_check@@LIBMNL_1.0
0000000000002fd8 T mnl_attr_put_u32@@LIBMNL_1.0
0000000000003170 T mnl_attr_put_u32_check@@LIBMNL_1.0
0000000000002ff8 T mnl_attr_put_u64@@LIBMNL_1.0
0000000000003190 T mnl_attr_put_u64_check@@LIBMNL_1.0
0000000000002f98 T mnl_attr_put_u8@@LIBMNL_1.0
0000000000003130 T mnl_attr_put_u8_check@@LIBMNL_1.0
0000000000002c48 T mnl_attr_type_valid@@LIBMNL_1.0
0000000000002c98 T mnl_attr_validate@@LIBMNL_1.0
0000000000002cd8 T mnl_attr_validate2@@LIBMNL_1.0
00000000000022f8 T mnl_cb_run@@LIBMNL_1.0
0000000000002168 T mnl_cb_run2@@LIBMNL_1.0
0000000000002ab0 T mnl_nlmsg_batch_current@@LIBMNL_1.0
0000000000002aa8 T mnl_nlmsg_batch_head@@LIBMNL_1.0
0000000000002ab8 T mnl_nlmsg_batch_is_empty@@LIBMNL_1.0
00000000000029f8 T mnl_nlmsg_batch_next@@LIBMNL_1.0
0000000000002a40 T mnl_nlmsg_batch_reset@@LIBMNL_1.0
0000000000002aa0 T mnl_nlmsg_batch_size@@LIBMNL_1.0
00000000000029b8 T mnl_nlmsg_batch_start@@LIBMNL_1.0
00000000000029f0 T mnl_nlmsg_batch_stop@@LIBMNL_1.0
0000000000002590 T mnl_nlmsg_fprintf@@LIBMNL_1.0
00000000000024c8 T mnl_nlmsg_get_payload@@LIBMNL_1.0
0000000000002470 T mnl_nlmsg_get_payload_len@@LIBMNL_1.0
00000000000024d0 T mnl_nlmsg_get_payload_offset@@LIBMNL_1.0
0000000000002548 T mnl_nlmsg_get_payload_tail@@LIBMNL_1.0
0000000000002518 T mnl_nlmsg_next@@LIBMNL_1.0
00000000000024e8 T mnl_nlmsg_ok@@LIBMNL_1.0
0000000000002578 T mnl_nlmsg_portid_ok@@LIBMNL_1.0
0000000000002490 T mnl_nlmsg_put_extra_header@@LIBMNL_1.0
0000000000002480 T mnl_nlmsg_put_header@@LIBMNL_1.0
0000000000002560 T mnl_nlmsg_seq_ok@@LIBMNL_1.0
0000000000002468 T mnl_nlmsg_size@@LIBMNL_1.0
0000000000001ec0 T mnl_socket_bind@@LIBMNL_1.0
0000000000002068 T mnl_socket_close@@LIBMNL_1.0
0000000000001e18 T mnl_socket_fdopen@@LIBMNL_1.2
0000000000001df8 T mnl_socket_get_fd@@LIBMNL_1.0
0000000000001e00 T mnl_socket_get_portid@@LIBMNL_1.0
00000000000020c0 T mnl_socket_getsockopt@@LIBMNL_1.0
0000000000001e08 T mnl_socket_open@@LIBMNL_1.0
0000000000001e10 T mnl_socket_open2@@LIBMNL_1.2
0000000000001fa0 T mnl_socket_recvfrom@@LIBMNL_1.0
0000000000001f88 T mnl_socket_sendto@@LIBMNL_1.0
00000000000020a0 T mnl_socket_setsockopt@@LIBMNL_1.0
$
8<----------------------------------------------------------------------
There were other problems when I tried the same thing on x86, but that
was gcc version 8, so I think they can be ignored.
gcc-8 should be fine. Please document these problems also.
8<----------------------------------------------------------------------
# uname -a
Linux laptop3 4.19.0-27-amd64 #1 SMP Debian 4.19.316-1 (2024-06-25) x86_64 GNU/Linux
# apt-get install libmnl-dev libmnl0 libnetfilter-queue-dev libnetfilter-queue1 libnftnl11 libnftnl-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
libmnl-dev is already the newest version (1.0.4-2).
libmnl0 is already the newest version (1.0.4-2).
libnetfilter-queue-dev is already the newest version (1.0.3-1).
libnetfilter-queue1 is already the newest version (1.0.3-1).
libnftnl-dev is already the newest version (1.1.2-2).
libnftnl11 is already the newest version (1.1.2-2).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
#
8<----------------------------------------------------------------------
8<----------------------------------------------------------------------
$ gcc -g3 -gdwarf-4 -lmnl -lnetfilter_queue -o nf-queue nf-queue.c
nf-queue.c: In function ʽnfq_send_verdictʼ:
nf-queue.c:30:8: warning: implicit declaration of function ʽnfq_nlmsg_putʼ; did you mean ʽnfq_nlmsg_parseʼ? [-Wimplicit-function-declaration]
nlh = nfq_nlmsg_put(buf, NFQNL_MSG_VERDICT, queue_num);
^~~~~~~~~~~~~
nfq_nlmsg_parse
nf-queue.c:30:6: warning: assignment to ʽstruct nlmsghdr *ʼ from ʽintʼ makes pointer from integer without a cast [-Wint-conversion]
nlh = nfq_nlmsg_put(buf, NFQNL_MSG_VERDICT, queue_num);
^
nf-queue.c: In function ʽmainʼ:
nf-queue.c:184:6: warning: assignment to ʽstruct nlmsghdr *ʼ from ʽintʼ makes pointer from integer without a cast [-Wint-conversion]
nlh = nfq_nlmsg_put(buf, NFQNL_MSG_CONFIG, queue_num);
^
nf-queue.c:195:6: warning: assignment to ʽstruct nlmsghdr *ʼ from ʽintʼ makes pointer from integer without a cast [-Wint-conversion]
nlh = nfq_nlmsg_put(buf, NFQNL_MSG_CONFIG, queue_num);
^
/usr/bin/ld: /tmp/cc2fCm9v.o: in function `nfq_send_verdict':
/home/ged/Downloads/src/net/netfilter/nf-queue.c:30: undefined reference to `nfq_nlmsg_put'
/usr/bin/ld: /tmp/cc2fCm9v.o: in function `main':
/home/ged/Downloads/src/net/netfilter/nf-queue.c:184: undefined reference to `nfq_nlmsg_put'
/usr/bin/ld: /home/ged/Downloads/src/net/netfilter/nf-queue.c:195: undefined reference to `nfq_nlmsg_put'
collect2: error: ld returned 1 exit status
$
8<----------------------------------------------------------------------
Changing the order of command line options doesn't seem to help.
8<----------------------------------------------------------------------
$ nm -D /usr/lib/x86_64-linux-gnu/libmnl.so|grep -Ew T
0000000000002f20 T mnl_attr_get_len
0000000000002fa0 T mnl_attr_get_payload
0000000000002f60 T mnl_attr_get_payload_len
0000000000003560 T mnl_attr_get_str
0000000000002ee0 T mnl_attr_get_type
00000000000034a0 T mnl_attr_get_u16
00000000000034e0 T mnl_attr_get_u32
0000000000003520 T mnl_attr_get_u64
0000000000003460 T mnl_attr_get_u8
0000000000003b80 T mnl_attr_nest_cancel
0000000000003b40 T mnl_attr_nest_end
0000000000003820 T mnl_attr_nest_start
0000000000003ae0 T mnl_attr_nest_start_check
0000000000003110 T mnl_attr_next
00000000000030c0 T mnl_attr_ok
0000000000003290 T mnl_attr_parse
0000000000003330 T mnl_attr_parse_nested
00000000000033e0 T mnl_attr_parse_payload
00000000000035a0 T mnl_attr_put
0000000000003870 T mnl_attr_put_check
0000000000003760 T mnl_attr_put_str
0000000000003a10 T mnl_attr_put_str_check
00000000000037c0 T mnl_attr_put_strz
0000000000003a70 T mnl_attr_put_strz_check
0000000000003670 T mnl_attr_put_u16
0000000000003920 T mnl_attr_put_u16_check
00000000000036c0 T mnl_attr_put_u32
0000000000003970 T mnl_attr_put_u32_check
0000000000003710 T mnl_attr_put_u64
00000000000039c0 T mnl_attr_put_u64_check
0000000000003620 T mnl_attr_put_u8
00000000000038d0 T mnl_attr_put_u8_check
0000000000003150 T mnl_attr_type_valid
00000000000031b0 T mnl_attr_validate
0000000000003220 T mnl_attr_validate2
0000000000002390 T mnl_cb_run
0000000000002200 T mnl_cb_run2
0000000000002e60 T mnl_nlmsg_batch_current
0000000000002e20 T mnl_nlmsg_batch_head
0000000000002ea0 T mnl_nlmsg_batch_is_empty
0000000000002d00 T mnl_nlmsg_batch_next
0000000000002d60 T mnl_nlmsg_batch_reset
0000000000002de0 T mnl_nlmsg_batch_size
0000000000002c60 T mnl_nlmsg_batch_start
0000000000002cc0 T mnl_nlmsg_batch_stop
0000000000002800 T mnl_nlmsg_fprintf
0000000000002600 T mnl_nlmsg_get_payload
0000000000002510 T mnl_nlmsg_get_payload_len
0000000000002640 T mnl_nlmsg_get_payload_offset
0000000000002720 T mnl_nlmsg_get_payload_tail
00000000000026d0 T mnl_nlmsg_next
0000000000002680 T mnl_nlmsg_ok
00000000000027b0 T mnl_nlmsg_portid_ok
00000000000025a0 T mnl_nlmsg_put_extra_header
0000000000002550 T mnl_nlmsg_put_header
0000000000002760 T mnl_nlmsg_seq_ok
00000000000024d0 T mnl_nlmsg_size
0000000000001e50 T mnl_socket_bind
0000000000002010 T mnl_socket_close
0000000000001dc0 T mnl_socket_fdopen
0000000000001cd0 T mnl_socket_get_fd
0000000000001d00 T mnl_socket_get_portid
00000000000020b0 T mnl_socket_getsockopt
0000000000001d40 T mnl_socket_open
0000000000001d80 T mnl_socket_open2
0000000000001f40 T mnl_socket_recvfrom
0000000000001ef0 T mnl_socket_sendto
0000000000002060 T mnl_socket_setsockopt
$
8<----------------------------------------------------------------------
Thanks for being interested. :)
--
73,
Ged.
