![Jesper Dangaard Brouer](/assets/img/avatar_default.png)
This address the TODO in samples/bpf/xdp_fwd_kern.c, which points out
that the chosen egress index should be checked for existence in the
devmap. This can now be done via taking advantage of Toke's work in
commit 0cdbb4b09a
("devmap: Allow map lookups from eBPF").
This change makes xdp_fwd more practically usable, as this allows for
a mixed environment, where IP-forwarding fallback to network stack, if
the egress device isn't configured to use XDP.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
160 lines
3.5 KiB
C
160 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2017-18 David Ahern <dsahern@gmail.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/bpf.h>
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#include <linux/if_link.h>
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#include <linux/limits.h>
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#include <net/if.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <libgen.h>
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#include "libbpf.h"
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#include <bpf/bpf.h>
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static int do_attach(int idx, int prog_fd, int map_fd, const char *name)
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{
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int err;
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err = bpf_set_link_xdp_fd(idx, prog_fd, 0);
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if (err < 0) {
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printf("ERROR: failed to attach program to %s\n", name);
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return err;
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}
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/* Adding ifindex as a possible egress TX port */
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err = bpf_map_update_elem(map_fd, &idx, &idx, 0);
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if (err)
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printf("ERROR: failed using device %s as TX-port\n", name);
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return err;
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}
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static int do_detach(int idx, const char *name)
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{
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int err;
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err = bpf_set_link_xdp_fd(idx, -1, 0);
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if (err < 0)
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printf("ERROR: failed to detach program from %s\n", name);
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/* TODO: Remember to cleanup map, when adding use of shared map
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* bpf_map_delete_elem((map_fd, &idx);
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*/
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return err;
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}
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static void usage(const char *prog)
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{
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fprintf(stderr,
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"usage: %s [OPTS] interface-list\n"
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"\nOPTS:\n"
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" -d detach program\n"
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" -D direct table lookups (skip fib rules)\n",
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prog);
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}
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int main(int argc, char **argv)
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{
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struct bpf_prog_load_attr prog_load_attr = {
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.prog_type = BPF_PROG_TYPE_XDP,
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};
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const char *prog_name = "xdp_fwd";
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struct bpf_program *prog;
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int prog_fd, map_fd = -1;
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char filename[PATH_MAX];
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struct bpf_object *obj;
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int opt, i, idx, err;
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int attach = 1;
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int ret = 0;
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while ((opt = getopt(argc, argv, ":dD")) != -1) {
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switch (opt) {
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case 'd':
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attach = 0;
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break;
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case 'D':
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prog_name = "xdp_fwd_direct";
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break;
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default:
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usage(basename(argv[0]));
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return 1;
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}
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}
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if (optind == argc) {
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usage(basename(argv[0]));
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return 1;
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}
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if (attach) {
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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prog_load_attr.file = filename;
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if (access(filename, O_RDONLY) < 0) {
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printf("error accessing file %s: %s\n",
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filename, strerror(errno));
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return 1;
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}
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err = bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd);
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if (err) {
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printf("Does kernel support devmap lookup?\n");
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/* If not, the error message will be:
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* "cannot pass map_type 14 into func bpf_map_lookup_elem#1"
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*/
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return 1;
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}
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prog = bpf_object__find_program_by_title(obj, prog_name);
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prog_fd = bpf_program__fd(prog);
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if (prog_fd < 0) {
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printf("program not found: %s\n", strerror(prog_fd));
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return 1;
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}
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map_fd = bpf_map__fd(bpf_object__find_map_by_name(obj,
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"xdp_tx_ports"));
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if (map_fd < 0) {
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printf("map not found: %s\n", strerror(map_fd));
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return 1;
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}
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}
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for (i = optind; i < argc; ++i) {
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idx = if_nametoindex(argv[i]);
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if (!idx)
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idx = strtoul(argv[i], NULL, 0);
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if (!idx) {
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fprintf(stderr, "Invalid arg\n");
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return 1;
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}
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if (!attach) {
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err = do_detach(idx, argv[i]);
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if (err)
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ret = err;
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} else {
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err = do_attach(idx, prog_fd, map_fd, argv[i]);
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if (err)
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ret = err;
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}
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}
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return ret;
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}
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