def nl_complete_msg(sk, msg):
"""Finalize Netlink message.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/nl.c#L450
This function finalizes a Netlink message by completing the message with desirable flags and values depending on the
socket configuration.
- If not yet filled out, the source address of the message (`nlmsg_pid`) will be set to the local port number of the
socket.
- If not yet specified, the next available sequence number is assigned to the message (`nlmsg_seq`).
- If not yet specified, the protocol field of the message will be set to the protocol field of the socket.
- The `NLM_F_REQUEST` Netlink message flag will be set.
- The `NLM_F_ACK` flag will be set if Auto-ACK mode is enabled on the socket.
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
msg -- Netlink message (nl_msg class instance).
"""
nlh = msg.nm_nlh
if nlh.nlmsg_pid == NL_AUTO_PORT:
nlh.nlmsg_pid = nl_socket_get_local_port(sk)
if nlh.nlmsg_seq == NL_AUTO_SEQ:
nlh.nlmsg_seq = sk.s_seq_next
sk.s_seq_next += 1
if msg.nm_protocol == -1:
msg.nm_protocol = sk.s_proto
nlh.nlmsg_flags |= NLM_F_REQUEST
if not sk.s_flags & NL_NO_AUTO_ACK:
nlh.nlmsg_flags |= NLM_F_ACK
def nl_complete_msg(sk, msg):
"""Finalize Netlink message.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/nl.c#L450
This function finalizes a Netlink message by completing the message with desirable flags and values depending on the
socket configuration.
- If not yet filled out, the source address of the message (`nlmsg_pid`) will be set to the local port number of the
socket.
- If not yet specified, the next available sequence number is assigned to the message (`nlmsg_seq`).
- If not yet specified, the protocol field of the message will be set to the protocol field of the socket.
- The `NLM_F_REQUEST` Netlink message flag will be set.
- The `NLM_F_ACK` flag will be set if Auto-ACK mode is enabled on the socket.
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
msg -- Netlink message (nl_msg class instance).
"""
nlh = msg.nm_nlh
if nlh.nlmsg_pid == NL_AUTO_PORT:
nlh.nlmsg_pid = nl_socket_get_local_port(sk)
if nlh.nlmsg_seq == NL_AUTO_SEQ:
nlh.nlmsg_seq = sk.s_seq_next
sk.s_seq_next += 1
if msg.nm_protocol == -1:
msg.nm_protocol = sk.s_proto
nlh.nlmsg_flags |= NLM_F_REQUEST
if not sk.s_flags & NL_NO_AUTO_ACK:
nlh.nlmsg_flags |= NLM_F_ACK
def test_defaults(log):
r"""C code to test against.
// gcc a.c $(pkg-config --cflags --libs libnl-genl-3.0) && NLDBG=4 ./a.out
#include <netlink/msg.h>
struct ucred { __u32 pid; __u32 uid; __u32 gid; };
struct nl_msg {
int nm_protocol; int nm_flags; struct sockaddr_nl nm_src; struct sockaddr_nl nm_dst; struct ucred nm_creds;
struct nlmsghdr *nm_nlh; size_t nm_size; int nm_refcnt;
};
struct nl_sock {
struct sockaddr_nl s_local; struct sockaddr_nl s_peer; int s_fd; int s_proto; unsigned int s_seq_next;
unsigned int s_seq_expect; int s_flags; struct nl_cb *s_cb; size_t s_bufsize;
};
void print(struct nl_msg *msg) {
printf("%d == msg.nm_protocol\n", msg->nm_protocol);
printf("%d == msg.nm_flags\n", msg->nm_flags);
printf("%d == msg.nm_src.nl_family\n", msg->nm_src.nl_family);
printf("%d == msg.nm_src.nl_pid\n", msg->nm_src.nl_pid);
printf("%d == msg.nm_src.nl_groups\n", msg->nm_src.nl_groups);
printf("%d == msg.nm_dst.nl_family\n", msg->nm_dst.nl_family);
printf("%d == msg.nm_dst.nl_pid\n", msg->nm_dst.nl_pid);
printf("%d == msg.nm_dst.nl_groups\n", msg->nm_dst.nl_groups);
printf("%d == msg.nm_nlh.nlmsg_type\n", msg->nm_nlh->nlmsg_type);
printf("%d == msg.nm_nlh.nlmsg_flags\n", msg->nm_nlh->nlmsg_flags);
printf("%d == msg.nm_nlh.nlmsg_pid\n", msg->nm_nlh->nlmsg_pid);
}
int main() {
printf("Begin main()\n");
struct nl_sock *sk = nl_socket_alloc();
printf("Allocated socket.\n");
struct nl_msg *msg = nlmsg_alloc_simple(0, 0);
printf("Allocated message.\n");
printf("%d == nl_socket_get_local_port(sk)\n", nl_socket_get_local_port(sk));
printf("%d == sk.s_proto\n", sk->s_proto);
printf("\n");
print(msg);
printf("\n");
nl_complete_msg(sk, msg);
print(msg);
return 0;
}
// Expected output (trimmed):
// nl_cache_mngt_register: Registered cache operations genl/family
// Begin main()
// Allocated socket.
// __nlmsg_alloc: msg 0x1e9c0b8: Allocated new message, maxlen=4096
// nlmsg_alloc_simple: msg 0x1e9c0b8: Allocated new simple message
// Allocated message.
// 10083 == nl_socket_get_local_port(sk)
// 0 == sk.s_proto
//
// -1 == msg.nm_protocol
// 0 == msg.nm_flags
// 0 == msg.nm_src.nl_family
// 0 == msg.nm_src.nl_pid
// 0 == msg.nm_src.nl_groups
// 0 == msg.nm_dst.nl_family
// 0 == msg.nm_dst.nl_pid
// 0 == msg.nm_dst.nl_groups
// 0 == msg.nm_nlh.nlmsg_type
// 0 == msg.nm_nlh.nlmsg_flags
// 0 == msg.nm_nlh.nlmsg_pid
//
// 0 == msg.nm_protocol
// 0 == msg.nm_flags
// 0 == msg.nm_src.nl_family
// 0 == msg.nm_src.nl_pid
// 0 == msg.nm_src.nl_groups
// 0 == msg.nm_dst.nl_family
// 0 == msg.nm_dst.nl_pid
// 0 == msg.nm_dst.nl_groups
// 0 == msg.nm_nlh.nlmsg_type
// 5 == msg.nm_nlh.nlmsg_flags
// 10083 == msg.nm_nlh.nlmsg_pid
// nl_cache_mngt_unregister: Unregistered cache operations genl/family
"""
del log[:]
sk = nl_socket_alloc()
msg = nlmsg_alloc_simple(0, 0)
assert re.match('nlmsg_alloc: msg 0x[a-f0-9]+: Allocated new message', log.pop(0))
assert re.match('nlmsg_alloc_simple: msg 0x[a-f0-9]+: Allocated new simple message', log.pop(0))
local_port = int(nl_socket_get_local_port(sk))
proto = int(sk.s_proto)
assert 0 < local_port
assert 0 == proto
assert -1 == msg.nm_protocol
assert 0 == msg.nm_flags
assert 0 == msg.nm_src.nl_family
assert 0 == msg.nm_src.nl_pid
assert 0 == msg.nm_src.nl_groups
assert 0 == msg.nm_dst.nl_family
assert 0 == msg.nm_dst.nl_pid
assert 0 == msg.nm_dst.nl_groups
assert 0 == msg.nm_nlh.nlmsg_type
assert 0 == msg.nm_nlh.nlmsg_flags
assert 0 == msg.nm_nlh.nlmsg_pid
nl_complete_msg(sk, msg)
assert proto == msg.nm_protocol
assert 0 == msg.nm_flags
assert 0 == msg.nm_src.nl_family
assert 0 == msg.nm_src.nl_pid
assert 0 == msg.nm_src.nl_groups
assert 0 == msg.nm_dst.nl_family
assert 0 == msg.nm_dst.nl_pid
assert 0 == msg.nm_dst.nl_groups
assert 0 == msg.nm_nlh.nlmsg_type
assert 5 == msg.nm_nlh.nlmsg_flags
assert local_port == msg.nm_nlh.nlmsg_pid
assert not log
nl_socket_free(sk)
