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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: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Daniel Borkmann 2019-08-09 18:05:03 +02:00
parent d9973cec9d abcce733ad
commit 9f30cd568b
2 changed files with 53 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
samples/bpf/xdp_fwd_kern.c
View File

@ -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
* cannot pass map_type 14 into func bpf_map_lookup_elem#1:
* NOTE: without verification that egress index supports XDP
* forwarding packets are dropped.
/*
* 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 == 0) {
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:
*/
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;

35
samples/bpf/xdp_fwd_user.c
View File

@ -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;
}