linux-brain/net/bpfilter/main.c

// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <sys/uio.h>
#include <errno.h>
#include <stdio.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <unistd.h>
#include "../../include/uapi/linux/bpf.h"
#include <asm/unistd.h>
#include "msgfmt.h"

FILE *debug_f;

static int handle_get_cmd(struct mbox_request *cmd)
{
	switch (cmd->cmd) {
	case 0:
		return 0;
	default:
		break;
	}
	return -ENOPROTOOPT;
}

static int handle_set_cmd(struct mbox_request *cmd)
{
	return -ENOPROTOOPT;
}

static void loop(void)
{
	while (1) {
		struct mbox_request req;
		struct mbox_reply reply;
		int n;

		n = read(0, &req, sizeof(req));
		if (n != sizeof(req)) {
			fprintf(debug_f, "invalid request %d\n", n);
			return;
		}

		reply.status = req.is_set ?
			handle_set_cmd(&req) :
			handle_get_cmd(&req);

		n = write(1, &reply, sizeof(reply));
		if (n != sizeof(reply)) {
			fprintf(debug_f, "reply failed %d\n", n);
			return;
		}
	}
}

int main(void)
{
	debug_f = fopen("/dev/kmsg", "w");
	setvbuf(debug_f, 0, _IOLBF, 0);
	fprintf(debug_f, "<5>Started bpfilter\n");
	loop();
	fclose(debug_f);
	return 0;
}