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Commit 9f30cd56 authored by Daniel Borkmann's avatar Daniel Borkmann
Browse files

Merge branch 'bpf-xdp-fwd-sample-improvements' 

Jesper Dangaard Brouer says:

====================
V3: Hopefully fixed all issues point out by Yonghong Song

V2: Addressed issues point out by Yonghong Song
 - Please ACK patch 2/3 again
 - Added ACKs and reviewed-by to other patches

This patchset is focused on improvements for XDP forwarding sample
named xdp_fwd, which leverage the existing FIB routing tables as
described in LPC2018[1] talk by David Ahern.

The primary motivation is to illustrate how Toke's recent work
improves usability of XDP_REDIRECT via lookups in devmap. The other
patches are to help users understand the sample.

I have more improvements to xdp_fwd, but those might requires changes
to libbpf.  Thus, sending these patches first as they are isolated.

[1] http://vger.kernel.org/lpc-networking2018.html#session-1


====================

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parents d9973cec abcce733

samples/bpf/xdp_fwd_kern.c

+30 −9
Original line number Diff line number Diff line
@@ -23,7 +23,8 @@ 


#define IPV6_FLOWINFO_MASK              cpu_to_be32(0x0FFFFFFF)



struct bpf_map_def SEC("maps") tx_port = {

/* For TX-traffic redirect requires net_device ifindex to be in this devmap */

struct bpf_map_def SEC("maps") xdp_tx_ports = {

	.type = BPF_MAP_TYPE_DEVMAP,

	.key_size = sizeof(int),

	.value_size = sizeof(int),
@@ -102,14 +103,34 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) 
	fib_params.ifindex = ctx->ingress_ifindex;



	rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);



	/* verify egress index has xdp support

	 * TO-DO bpf_map_lookup_elem(&tx_port, &key) fails with

	/*

	 * Some rc (return codes) from bpf_fib_lookup() are important,

	 * to understand how this XDP-prog interacts with network stack.

	 *

	 * BPF_FIB_LKUP_RET_NO_NEIGH:

	 *  Even if route lookup was a success, then the MAC-addresses are also

	 *  needed.  This is obtained from arp/neighbour table, but if table is

	 *  (still) empty then BPF_FIB_LKUP_RET_NO_NEIGH is returned.  To avoid

	 *  doing ARP lookup directly from XDP, then send packet to normal

	 *  network stack via XDP_PASS and expect it will do ARP resolution.

	 *

	 * BPF_FIB_LKUP_RET_FWD_DISABLED:

	 *  The bpf_fib_lookup respect sysctl net.ipv{4,6}.conf.all.forwarding

	 *  setting, and will return BPF_FIB_LKUP_RET_FWD_DISABLED if not

	 *  enabled this on ingress device.

	 */

	if (rc == BPF_FIB_LKUP_RET_SUCCESS) {

		/* Verify egress index has been configured as TX-port.

		 * (Note: User can still have inserted an egress ifindex that

		 * doesn't support XDP xmit, which will result in packet drops).

		 *

		 * Note: lookup in devmap supported since 0cdbb4b09a0.

		 * If not supported will fail with:

		 *  cannot pass map_type 14 into func bpf_map_lookup_elem#1:

	 * NOTE: without verification that egress index supports XDP

	 *       forwarding packets are dropped.

		 */

	if (rc == 0) {

		if (!bpf_map_lookup_elem(&xdp_tx_ports, &fib_params.ifindex))

			return XDP_PASS;



		if (h_proto == htons(ETH_P_IP))

			ip_decrease_ttl(iph);

		else if (h_proto == htons(ETH_P_IPV6))
@@ -117,7 +138,7 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) 


		memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);

		memcpy(eth->h_source, fib_params.smac, ETH_ALEN);

		return bpf_redirect_map(&tx_port, fib_params.ifindex, 0);

		return bpf_redirect_map(&xdp_tx_ports, fib_params.ifindex, 0);

	}



	return XDP_PASS;

samples/bpf/xdp_fwd_user.c

+23 −12
Original line number Diff line number Diff line
@@ -27,14 +27,20 @@ 
#include "libbpf.h"

#include <bpf/bpf.h>





static int do_attach(int idx, int fd, const char *name)

static int do_attach(int idx, int prog_fd, int map_fd, const char *name)

{

	int err;



	err = bpf_set_link_xdp_fd(idx, fd, 0);

	if (err < 0)

	err = bpf_set_link_xdp_fd(idx, prog_fd, 0);

	if (err < 0) {

		printf("ERROR: failed to attach program to %s\n", name);

		return err;

	}



	/* Adding ifindex as a possible egress TX port */

	err = bpf_map_update_elem(map_fd, &idx, &idx, 0);

	if (err)

		printf("ERROR: failed using device %s as TX-port\n", name);



	return err;

}
@@ -47,6 +53,9 @@ static int do_detach(int idx, const char *name) 
	if (err < 0)

		printf("ERROR: failed to detach program from %s\n", name);



	/* TODO: Remember to cleanup map, when adding use of shared map

	 *  bpf_map_delete_elem((map_fd, &idx);

	 */

	return err;

}
@@ -67,10 +76,10 @@ int main(int argc, char **argv) 
	};

	const char *prog_name = "xdp_fwd";

	struct bpf_program *prog;

	int prog_fd, map_fd = -1;

	char filename[PATH_MAX];

	struct bpf_object *obj;

	int opt, i, idx, err;

	int prog_fd, map_fd;

	int attach = 1;

	int ret = 0;
@@ -103,8 +112,14 @@ int main(int argc, char **argv) 
			return 1;

		}



		if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))

		err = bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd);

		if (err) {

			printf("Does kernel support devmap lookup?\n");

			/* If not, the error message will be:

			 *  "cannot pass map_type 14 into func bpf_map_lookup_elem#1"

			 */

			return 1;

		}



		prog = bpf_object__find_program_by_title(obj, prog_name);

		prog_fd = bpf_program__fd(prog);
@@ -113,16 +128,12 @@ int main(int argc, char **argv) 
			return 1;

		}

		map_fd = bpf_map__fd(bpf_object__find_map_by_name(obj,

								  "tx_port"));

							"xdp_tx_ports"));

		if (map_fd < 0) {

			printf("map not found: %s\n", strerror(map_fd));

			return 1;

		}

	}

	if (attach) {

		for (i = 1; i < 64; ++i)

			bpf_map_update_elem(map_fd, &i, &i, 0);

	}



	for (i = optind; i < argc; ++i) {

		idx = if_nametoindex(argv[i]);
@@ -138,7 +149,7 @@ int main(int argc, char **argv) 
			if (err)

				ret = err;

		} else {

			err = do_attach(idx, prog_fd, argv[i]);

			err = do_attach(idx, prog_fd, map_fd, argv[i]);

			if (err)

				ret = err;

		}