samples/bpf: Attach XDP programs in driver mode by default

When attaching XDP programs, userspace can set flags to request the attach
mode (generic/SKB mode, driver mode or hw offloaded mode). If no such flags
are requested, the kernel will attempt to attach in driver mode, and then
silently fall back to SKB mode if this fails.

The silent fallback is a major source of user confusion, as users will try
to load a program on a device without XDP support, and instead of an error
they will get the silent fallback behaviour, not notice, and then wonder
why performance is not what they were expecting.

In an attempt to combat this, let's switch all the samples to default to
explicitly requesting driver-mode attach. As part of this, ensure that all
the userspace utilities have a switch to enable SKB mode. For those that
have a switch to request driver mode, keep it but turn it into a no-op.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: David Ahern <dsahern@gmail.com>
Link: https://lore.kernel.org/bpf/20191216110742.364456-1-toke@redhat.com

diff --git a/samples/bpf/xdp1_user.c b/samples/bpf/xdp1_user.c
index 3e553ee..38a8852 100644 (file)
--- a/samples/bpf/xdp1_user.c
+++ b/samples/bpf/xdp1_user.c
@@ -98,7 +98,7 @@ int main(int argc, char **argv)
                        xdp_flags |= XDP_FLAGS_SKB_MODE;
                        break;
                case 'N':
-                       xdp_flags |= XDP_FLAGS_DRV_MODE;
+                       /* default, set below */
                        break;
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
@@ -109,6 +109,9 @@ int main(int argc, char **argv)
                }
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        if (optind == argc) {
                usage(basename(argv[0]));
                return 1;

diff --git a/samples/bpf/xdp_adjust_tail_user.c b/samples/bpf/xdp_adjust_tail_user.c
index d86e9ad..008789e 100644 (file)
--- a/samples/bpf/xdp_adjust_tail_user.c
+++ b/samples/bpf/xdp_adjust_tail_user.c
@@ -120,7 +120,7 @@ int main(int argc, char **argv)
                        xdp_flags |= XDP_FLAGS_SKB_MODE;
                        break;
                case 'N':
-                       xdp_flags |= XDP_FLAGS_DRV_MODE;
+                       /* default, set below */
                        break;
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
@@ -132,6 +132,9 @@ int main(int argc, char **argv)
                opt_flags[opt] = 0;
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        for (i = 0; i < strlen(optstr); i++) {
                if (opt_flags[(unsigned int)optstr[i]]) {
                        fprintf(stderr, "Missing argument -%c\n", optstr[i]);

diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c
index 97ff1da..c30f9ac 100644 (file)
--- a/samples/bpf/xdp_fwd_user.c
+++ b/samples/bpf/xdp_fwd_user.c
@@ -27,11 +27,13 @@
 #include "libbpf.h"
 #include <bpf/bpf.h>
 
+static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
+
 static int do_attach(int idx, int prog_fd, int map_fd, const char *name)
 {
        int err;
 
-       err = bpf_set_link_xdp_fd(idx, prog_fd, 0);
+       err = bpf_set_link_xdp_fd(idx, prog_fd, xdp_flags);
        if (err < 0) {
                printf("ERROR: failed to attach program to %s\n", name);
                return err;
@@ -49,7 +51,7 @@ static int do_detach(int idx, const char *name)
 {
        int err;
 
-       err = bpf_set_link_xdp_fd(idx, -1, 0);
+       err = bpf_set_link_xdp_fd(idx, -1, xdp_flags);
        if (err < 0)
                printf("ERROR: failed to detach program from %s\n", name);
 
@@ -83,11 +85,17 @@ int main(int argc, char **argv)
        int attach = 1;
        int ret = 0;
 
-       while ((opt = getopt(argc, argv, ":dD")) != -1) {
+       while ((opt = getopt(argc, argv, ":dDSF")) != -1) {
                switch (opt) {
                case 'd':
                        attach = 0;
                        break;
+               case 'S':
+                       xdp_flags |= XDP_FLAGS_SKB_MODE;
+                       break;
+               case 'F':
+                       xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
+                       break;
                case 'D':
                        prog_name = "xdp_fwd_direct";
                        break;
@@ -97,6 +105,9 @@ int main(int argc, char **argv)
                }
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        if (optind == argc) {
                usage(basename(argv[0]));
                return 1;

diff --git a/samples/bpf/xdp_redirect_cpu_user.c b/samples/bpf/xdp_redirect_cpu_user.c
index 0da6e9e..72af628 100644 (file)
--- a/samples/bpf/xdp_redirect_cpu_user.c
+++ b/samples/bpf/xdp_redirect_cpu_user.c
@@ -728,6 +728,10 @@ int main(int argc, char **argv)
                        return EXIT_FAIL_OPTION;
                }
        }
+
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        /* Required option */
        if (ifindex == -1) {
                fprintf(stderr, "ERR: required option --dev missing\n");

diff --git a/samples/bpf/xdp_redirect_map_user.c b/samples/bpf/xdp_redirect_map_user.c
index f70ee33..cc84066 100644 (file)
--- a/samples/bpf/xdp_redirect_map_user.c
+++ b/samples/bpf/xdp_redirect_map_user.c
@@ -116,7 +116,7 @@ int main(int argc, char **argv)
                        xdp_flags |= XDP_FLAGS_SKB_MODE;
                        break;
                case 'N':
-                       xdp_flags |= XDP_FLAGS_DRV_MODE;
+                       /* default, set below */
                        break;
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
@@ -127,6 +127,9 @@ int main(int argc, char **argv)
                }
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        if (optind == argc) {
                printf("usage: %s <IFNAME|IFINDEX>_IN <IFNAME|IFINDEX>_OUT\n", argv[0]);
                return 1;

diff --git a/samples/bpf/xdp_redirect_user.c b/samples/bpf/xdp_redirect_user.c
index 5440cd6..71dff8e 100644 (file)
--- a/samples/bpf/xdp_redirect_user.c
+++ b/samples/bpf/xdp_redirect_user.c
@@ -117,7 +117,7 @@ int main(int argc, char **argv)
                        xdp_flags |= XDP_FLAGS_SKB_MODE;
                        break;
                case 'N':
-                       xdp_flags |= XDP_FLAGS_DRV_MODE;
+                       /* default, set below */
                        break;
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
@@ -128,6 +128,9 @@ int main(int argc, char **argv)
                }
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        if (optind == argc) {
                printf("usage: %s <IFNAME|IFINDEX>_IN <IFNAME|IFINDEX>_OUT\n", argv[0]);
                return 1;

diff --git a/samples/bpf/xdp_router_ipv4_user.c b/samples/bpf/xdp_router_ipv4_user.c
index 1469b66..fef286c 100644 (file)
--- a/samples/bpf/xdp_router_ipv4_user.c
+++ b/samples/bpf/xdp_router_ipv4_user.c
@@ -662,6 +662,9 @@ int main(int ac, char **argv)
                }
        }
 
+       if (!(flags & XDP_FLAGS_SKB_MODE))
+               flags |= XDP_FLAGS_DRV_MODE;
+
        if (optind == ac) {
                usage(basename(argv[0]));
                return 1;

diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
index 8fc3ad0..fc4983f 100644 (file)
--- a/samples/bpf/xdp_rxq_info_user.c
+++ b/samples/bpf/xdp_rxq_info_user.c
@@ -551,6 +551,10 @@ int main(int argc, char **argv)
                        return EXIT_FAIL_OPTION;
                }
        }
+
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        /* Required option */
        if (ifindex == -1) {
                fprintf(stderr, "ERR: required option --dev missing\n");

diff --git a/samples/bpf/xdp_sample_pkts_user.c b/samples/bpf/xdp_sample_pkts_user.c
index a5760e8..8c1af1b 100644 (file)
--- a/samples/bpf/xdp_sample_pkts_user.c
+++ b/samples/bpf/xdp_sample_pkts_user.c
@@ -52,13 +52,13 @@ static int do_detach(int idx, const char *name)
        __u32 curr_prog_id = 0;
        int err = 0;
 
-       err = bpf_get_link_xdp_id(idx, &curr_prog_id, 0);
+       err = bpf_get_link_xdp_id(idx, &curr_prog_id, xdp_flags);
        if (err) {
                printf("bpf_get_link_xdp_id failed\n");
                return err;
        }
        if (prog_id == curr_prog_id) {
-               err = bpf_set_link_xdp_fd(idx, -1, 0);
+               err = bpf_set_link_xdp_fd(idx, -1, xdp_flags);
                if (err < 0)
                        printf("ERROR: failed to detach prog from %s\n", name);
        } else if (!curr_prog_id) {
@@ -115,7 +115,7 @@ int main(int argc, char **argv)
                .prog_type      = BPF_PROG_TYPE_XDP,
        };
        struct perf_buffer_opts pb_opts = {};
-       const char *optstr = "F";
+       const char *optstr = "FS";
        int prog_fd, map_fd, opt;
        struct bpf_object *obj;
        struct bpf_map *map;
@@ -127,12 +127,18 @@ int main(int argc, char **argv)
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
                        break;
+               case 'S':
+                       xdp_flags |= XDP_FLAGS_SKB_MODE;
+                       break;
                default:
                        usage(basename(argv[0]));
                        return 1;
                }
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        if (optind == argc) {
                usage(basename(argv[0]));
                return 1;

diff --git a/samples/bpf/xdp_tx_iptunnel_user.c b/samples/bpf/xdp_tx_iptunnel_user.c
index 2fe4c7f..5f33b55 100644 (file)
--- a/samples/bpf/xdp_tx_iptunnel_user.c
+++ b/samples/bpf/xdp_tx_iptunnel_user.c
@@ -231,7 +231,7 @@ int main(int argc, char **argv)
                        xdp_flags |= XDP_FLAGS_SKB_MODE;
                        break;
                case 'N':
-                       xdp_flags |= XDP_FLAGS_DRV_MODE;
+                       /* default, set below */
                        break;
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
@@ -243,6 +243,9 @@ int main(int argc, char **argv)
                opt_flags[opt] = 0;
        }
 
+       if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+               xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        for (i = 0; i < strlen(optstr); i++) {
                if (opt_flags[(unsigned int)optstr[i]]) {
                        fprintf(stderr, "Missing argument -%c\n", optstr[i]);

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index a154800..e7829e5 100644 (file)
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -440,7 +440,7 @@ static void parse_command_line(int argc, char **argv)
                        opt_xdp_bind_flags |= XDP_COPY;
                        break;
                case 'N':
-                       opt_xdp_flags |= XDP_FLAGS_DRV_MODE;
+                       /* default, set below */
                        break;
                case 'n':
                        opt_interval = atoi(optarg);
@@ -474,6 +474,9 @@ static void parse_command_line(int argc, char **argv)
                }
        }
 
+       if (!(opt_xdp_flags & XDP_FLAGS_SKB_MODE))
+               opt_xdp_flags |= XDP_FLAGS_DRV_MODE;
+
        opt_ifindex = if_nametoindex(opt_if);
        if (!opt_ifindex) {
                fprintf(stderr, "ERROR: interface \"%s\" does not exist\n",