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https://github.com/xdp-project/bpf-examples.git
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Add DHCP relay program.
Initial working version of DHCP relay using XDP is created. Currently, this code has user program and a xdp ebpf program. User program takes network interface and dhcp relay server IP as inputs and store it in a map. XDP program filters the incoming DHCP requests and inserts option 82 in the DHCP request packets and overwrites the destination IP to that of DHCP relay server IP.An optional argu -ment for user program is also provided to unload the xdp program. README file provides to instructions to build and load the xdp program. Signed-off-by: Sachin Tiptur <sachin.tiptur.satyanarayana.gupta@hof-university.de> [ whitespace fixes ] Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
This commit is contained in:
Sachin Tiptur
committed by
Toke Høiland-Jørgensen
Toke Høiland-Jørgensen
parent
7bb3c6ac91
commit
cb9fc3025a
198
dhcp-relay/dhcp_user_xdp.c
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198
dhcp-relay/dhcp_user_xdp.c
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/* SPDX-License-Identifier: GPL-2.0 */
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static const char *__doc__ = "DHCP relay program to add Option 82\n";
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <getopt.h>
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#include <bpf/bpf.h>
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#include <bpf/libbpf.h>
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#include <net/if.h>
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#include <linux/if_link.h> /* depend on kernel-headers installed */
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#include <arpa/inet.h>
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#define SERVER_MAP "dhcp_server"
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#define XDP_OBJ "dhcp_kern_xdp.o"
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static const struct option options[] = {
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{ "help", no_argument, NULL, 'h' },
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{ "interface", required_argument, NULL,
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'i' }, // Name of interface to run on
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{ "dhcp-server", required_argument, NULL, 'd' },
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{ "mode", required_argument, NULL, 'm' },
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{ "unload", no_argument, NULL, 'u' },
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{ 0, 0, NULL, 0 }
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};
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static void print_usage(char *argv[])
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{
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int i;
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printf("Usage:\n");
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printf("%s\n", argv[0]);
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for (i = 0; options[i].name != 0; i++) {
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printf(" --%-12s", options[i].name);
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if (options[i].flag != NULL)
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printf(" flag (internal value:%d)", *options[i].flag);
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else
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printf(" short-option: -%c", options[i].val);
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printf("\n");
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}
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printf("Example:\n");
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printf("To load program:\n %s -i eth0 -d 10.0.0.1\n", argv[0]);
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printf("To unload program:\n %s -i eth0 -u\n", argv[0]);
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printf("\n");
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}
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static int xdp_link_detach(int ifindex, __u32 xdp_flags)
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{
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int err;
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if ((err = bpf_set_link_xdp_fd(ifindex, -1, xdp_flags)) < 0) {
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fprintf(stderr, "ERR: link set xdp unload failed (err=%d):%s\n",
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err, strerror(-err));
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return -1;
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}
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return 0;
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}
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int xdp_link_attach(int ifindex, __u32 xdp_flags, int prog_fd)
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{
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int err;
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/* libbpf provide the XDP net_device link-level hook attach helper */
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err = bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags);
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if (err < 0) {
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fprintf(stderr,
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"ERR: "
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"ifindex(%d) link set xdp fd failed (%d): %s\n",
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ifindex, -err, strerror(-err));
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switch (-err) {
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case EBUSY:
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case EEXIST:
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fprintf(stderr, "Hint: XDP already loaded on device\n");
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break;
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case EOPNOTSUPP:
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fprintf(stderr, "Hint: Native-XDP not supported\n");
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break;
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default:
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break;
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}
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return -1;
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}
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return 0;
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}
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/* User program takes two or three arguments
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* interface name, relay server IP and prog
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* unload flag
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*/
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int main(int argc, char **argv)
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{
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char filename[256] = "dhcp_kern_xdp.o";
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int prog_fd, err;
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int opt;
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__u32 xdp_flags = XDP_FLAGS_DRV_MODE;
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char dev[IF_NAMESIZE] = "";
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bool do_unload = 0;
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struct bpf_map *map = NULL;
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struct bpf_obj *obj = NULL;
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int map_fd;
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int key = 0;
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char server[15] = "";
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struct in_addr addr;
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__u16 ifindex;
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while ((opt = getopt_long(argc, argv, "hui:d:m:", options, NULL)) !=
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-1) {
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switch (opt) {
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case 'i':
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strncpy(dev, optarg, IF_NAMESIZE);
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dev[IF_NAMESIZE - 1] = '\0';
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ifindex = if_nametoindex(dev);
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if (ifindex <= 0) {
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printf("Couldn't find ifname:%s \n", dev);
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return -EINVAL;
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}
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break;
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case 'd':
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if (inet_aton(optarg, &addr) == 0) {
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fprintf(stderr,
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"Couldn't validate IP address:%s\n",
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optarg);
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return -EINVAL;
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}
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break;
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case 'm':
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if (strcmp(optarg, "skb") == 0) {
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xdp_flags = XDP_FLAGS_SKB_MODE;
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} else if (strcmp(optarg, "drv") != 0) {
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fprintf(stderr, "Invalid mode: %s\n", optarg);
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return -EINVAL;
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}
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break;
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case 'u':
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do_unload = 1;
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break;
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case 'h':
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print_usage(argv);
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exit(0);
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default:
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fprintf(stderr, "Unknown option %s\n", argv[optind]);
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return -EINVAL;
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}
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}
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if (do_unload)
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return xdp_link_detach(ifindex, xdp_flags);
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/* Load the BPF-ELF object file and get back first BPF_prog FD */
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err = bpf_prog_load(filename, BPF_PROG_TYPE_XDP, &obj, &prog_fd);
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if (err) {
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fprintf(stderr, "ERR: loading BPF-OBJ file(%s) (%d): %s\n",
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filename, err, strerror(-err));
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return -1;
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}
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if (prog_fd <= 0) {
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printf("ERR: loading file: %s\n");
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return -1;
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}
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/* read the map from prog object file and update the real
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* server IP to the map
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*/
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map = bpf_object__find_map_by_name(obj, SERVER_MAP);
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err = libbpf_get_error(map);
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if (err) {
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fprintf(stderr, "Could not find map %s in %s: %s\n", SERVER_MAP,
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XDP_OBJ, strerror(err));
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map = NULL;
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exit(-1);
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}
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map_fd = bpf_map__fd(map);
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if (map_fd < 0) {
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fprintf(stderr, "Could not get map fd\n");
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exit(-1);
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}
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err = bpf_map_update_elem(map_fd, &key, &addr.s_addr, BPF_ANY);
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if (err) {
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fprintf(stderr, "Could not update map %s in %s\n", SERVER_MAP,
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XDP_OBJ);
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exit(-1);
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}
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err = xdp_link_attach(ifindex, xdp_flags, prog_fd);
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if (err)
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return err;
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printf("Success: Loading xdp program\n");
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return 0;
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}
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