On Tue, 8 Dec 2020 16:18:56 +0800
Hangbin Liu <liuhangbin@xxxxxxxxx> wrote:
> This patch add a xdp program on egress to show that we can modify
> the packet on egress. In this sample we will set the pkt's src
> mac to egress's mac address. The xdp_prog will be attached when
> -X option supplied.
>
> Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
> ---
> v3:
> a) modify the src mac address based on egress mac
>
> v2:
> a) use pkt counter instead of IP ttl modification on egress program
> b) make the egress program selectable by option -X
> ---
> samples/bpf/xdp_redirect_map_kern.c | 60 ++++++++++-
> samples/bpf/xdp_redirect_map_user.c | 153 ++++++++++++++++++++--------
> 2 files changed, 168 insertions(+), 45 deletions(-)
>
[...]
> diff --git a/samples/bpf/xdp_redirect_map_user.c b/samples/bpf/xdp_redirect_map_user.c
> index 31131b6e7782..19636045c8dc 100644
> --- a/samples/bpf/xdp_redirect_map_user.c
> +++ b/samples/bpf/xdp_redirect_map_user.c
> @@ -14,6 +14,10 @@
> #include <unistd.h>
> #include <libgen.h>
> #include <sys/resource.h>
> +#include <sys/ioctl.h>
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +#include <netinet/in.h>
>
> #include "bpf_util.h"
> #include <bpf/bpf.h>
> @@ -21,7 +25,8 @@
>
> static int ifindex_in;
> static int ifindex_out;
> -static bool ifindex_out_xdp_dummy_attached = true;
> +static bool ifindex_out_xdp_dummy_attached = false;
> +static bool xdp_devmap_attached = false;
> static __u32 prog_id;
> static __u32 dummy_prog_id;
>
> @@ -83,6 +88,29 @@ static void poll_stats(int interval, int ifindex)
> }
> }
>
> +static int get_mac_addr(unsigned int ifindex_out, void *mac_addr)
> +{
> + struct ifreq ifr;
> + char ifname[IF_NAMESIZE];
> + int fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
I would have expected (like ethtool):
fd = socket(AF_INET, SOCK_DGRAM, 0);
> + if (fd < 0)
> + return -1;
> +
> + if (!if_indextoname(ifindex_out, ifname))
> + return -1;
> +
> + strcpy(ifr.ifr_name, ifname);
> +
> + if (ioctl(fd, SIOCGIFHWADDR, &ifr) != 0)
> + return -1;
> +
> + memcpy(mac_addr, ifr.ifr_hwaddr.sa_data, 6 * sizeof(char));
> + close(fd);
> +
> + return 0;
> +}
[...]
> - /* Loading dummy XDP prog on out-device */
> - if (bpf_set_link_xdp_fd(ifindex_out, dummy_prog_fd,
> - (xdp_flags | XDP_FLAGS_UPDATE_IF_NOEXIST)) < 0) {
> - printf("WARN: link set xdp fd failed on %d\n", ifindex_out);
> - ifindex_out_xdp_dummy_attached = false;
> - }
> + /* If -X supplied, load 2nd xdp prog on egress.
> + * If not, just load dummy prog on egress.
> + */
The dummy prog need to be loaded, regardless of 2nd xdp prog on egress.
> + if (xdp_devmap_attached) {
> + unsigned char mac_addr[6];
>
> - memset(&info, 0, sizeof(info));
> - ret = bpf_obj_get_info_by_fd(dummy_prog_fd, &info, &info_len);
> - if (ret) {
> - printf("can't get prog info - %s\n", strerror(errno));
> - return ret;
> + devmap_prog = bpf_object__find_program_by_title(obj, "xdp_devmap/map_prog");
> + if (!devmap_prog) {
> + printf("finding devmap_prog in obj file failed\n");
> + goto out;
> + }
> + devmap_prog_fd = bpf_program__fd(devmap_prog);
> + if (devmap_prog_fd < 0) {
> + printf("finding devmap_prog fd failed\n");
> + goto out;
> + }
> +
> + if (get_mac_addr(ifindex_out, mac_addr) < 0) {
> + printf("get interface %d mac failed\n", ifindex_out);
> + goto out;
> + }
> +
> + ret = bpf_map_update_elem(tx_mac_map_fd, &key, mac_addr, 0);
> + if (ret) {
> + perror("bpf_update_elem tx_mac_map_fd");
> + goto out;
> + }
> + } else if (ifindex_in != ifindex_out) {
> + dummy_prog = bpf_object__find_program_by_title(obj, "xdp_redirect_dummy");
> + if (!dummy_prog) {
> + printf("finding dummy_prog in obj file failed\n");
> + goto out;
> + }
> +
> + dummy_prog_fd = bpf_program__fd(dummy_prog);
> + if (dummy_prog_fd < 0) {
> + printf("find dummy_prog fd failed\n");
> + goto out;
> + }
> +
> + if (bpf_set_link_xdp_fd(ifindex_out, dummy_prog_fd,
> + (xdp_flags | XDP_FLAGS_UPDATE_IF_NOEXIST)) == 0) {
> + ifindex_out_xdp_dummy_attached = true;
> + } else {
> + printf("WARN: link set xdp fd failed on %d\n", ifindex_out);
> + }
> +
> + memset(&info, 0, sizeof(info));
> + ret = bpf_obj_get_info_by_fd(dummy_prog_fd, &info, &info_len);
> + if (ret) {
> + printf("can't get prog info - %s\n", strerror(errno));
> + }
> + dummy_prog_id = info.id;
> }
> - dummy_prog_id = info.id;
>
> signal(SIGINT, int_exit);
> signal(SIGTERM, int_exit);
>
> - /* populate virtual to physical port map */
> - ret = bpf_map_update_elem(tx_port_map_fd, &key, &ifindex_out, 0);
> + devmap_val.ifindex = ifindex_out;
> + devmap_val.bpf_prog.fd = devmap_prog_fd;
> + ret = bpf_map_update_elem(tx_port_map_fd, &key, &devmap_val, 0);
> if (ret) {
> - perror("bpf_update_elem");
> + perror("bpf_update_elem tx_port_map_fd");
> goto out;
> }
>
> poll_stats(2, ifindex_out);
>
> out:
> - return 0;
> + bpf_object__close(obj);
> + return 1;
> }
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
