3rd-party/linux-kernel-module-cheat
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netlink

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Ciro Santilli
2018-04-20 17:51:17 +01:00
parent 05888ec5c1
commit 4e0d9af81f
6 changed files with 146 additions and 16 deletions
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3
kernel_module/user/README.adoc
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@@ -25,5 +25,6 @@ These programs can also be compiled and used on host.
... link:ring0.c[]
. Module tests
.. link:anonymous_inode.c[]
.. link:poll.c[]
.. link:ioctl.c[]
.. link:netlink.c[]
.. link:poll.c[]

49
kernel_module/user/netlink.c Normal file
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@@ -0,0 +1,49 @@
#include <linux/netlink.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#define MAX_PAYLOAD 1024
#define NETLINK_USER 31
/* Some of these structs fields must be zeroed.
* We could brute force memset them, but
* TODO determine exactly which, and move into main. */
int sock_fd;
struct iovec iov;
struct msghdr msg;
struct nlmsghdr *nlh;
struct sockaddr_nl src_addr, dest_addr;
int main()
{
sock_fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_USER);
if (sock_fd < 0) {
perror("socket");
return EXIT_FAILURE;
}
src_addr.nl_family = AF_NETLINK;
src_addr.nl_pid = getpid();
bind(sock_fd, (struct sockaddr *)&src_addr, sizeof(src_addr));
dest_addr.nl_family = AF_NETLINK;
nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD));
memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));
nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
nlh->nlmsg_pid = getpid();
nlh->nlmsg_flags = 0;
strcpy(NLMSG_DATA(nlh), "user request");
iov.iov_base = (void *)nlh;
iov.iov_len = nlh->nlmsg_len;
msg.msg_name = (void *)&dest_addr;
msg.msg_namelen = sizeof(dest_addr);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
printf("before sendmsg\n");
sendmsg(sock_fd, &msg, 0);
printf("after sendmsg\n");
recvmsg(sock_fd, &msg, 0);
printf("userland received: %s\n", (char *)NLMSG_DATA(nlh));
close(sock_fd);
}