Subject: Re: [PATCH bpf-next 2/5] samples/bpf: add XDP_SHARED_UMEM support to xdpsock

From: William Tu <[email-masked]>
Date: Fri, 8 Nov 2019 11:09:30 -0800

On Fri, Nov 08, 2019 at 07:33:40PM +0100, Magnus Karlsson wrote:
> On Fri, Nov 8, 2019 at 7:15 PM William Tu <[email-masked]> wrote:
> >
> > On Thu, Nov 07, 2019 at 06:47:37PM +0100, Magnus Karlsson wrote:
> > > Add support for the XDP_SHARED_UMEM mode to the xdpsock sample
> > > application. As libbpf does not have a built in XDP program for this
> > > mode, we use an explicitly loaded XDP program. This also serves as an
> > > example on how to write your own XDP program that can route to an
> > > AF_XDP socket.
> > >
> > > Signed-off-by: Magnus Karlsson <[email-masked]>
> > > ---
> > >  samples/bpf/Makefile       |   1 +
> > >  samples/bpf/xdpsock.h      |  11 ++++
> > >  samples/bpf/xdpsock_kern.c |  24 ++++++++
> > >  samples/bpf/xdpsock_user.c | 141 +++++++++++++++++++++++++++++++--------------
> > >  4 files changed, 135 insertions(+), 42 deletions(-)
> > >  create mode 100644 samples/bpf/xdpsock.h
> > >  create mode 100644 samples/bpf/xdpsock_kern.c
> > >
> > > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> > > index 4df11dd..8a9af3a 100644
> > > --- a/samples/bpf/Makefile
> > > +++ b/samples/bpf/Makefile
> > > @@ -167,6 +167,7 @@ always += xdp_sample_pkts_kern.o
> > >  always += ibumad_kern.o
> > >  always += hbm_out_kern.o
> > >  always += hbm_edt_kern.o
> > > +always += xdpsock_kern.o
> > >
> > >  ifeq ($(ARCH), arm)
> > >  # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
> > > diff --git a/samples/bpf/xdpsock.h b/samples/bpf/xdpsock.h
> > > new file mode 100644
> > > index 0000000..b7eca15
> > > --- /dev/null
> > > +++ b/samples/bpf/xdpsock.h
> > > @@ -0,0 +1,11 @@
> > > +/* SPDX-License-Identifier: GPL-2.0
> > > + *
> > > + * Copyright(c) 2019 Intel Corporation.
> > > + */
> > > +
> > > +#ifndef XDPSOCK_H_
> > > +#define XDPSOCK_H_
> > > +
> > > +#define MAX_SOCKS 4
> > > +
> > > +#endif /* XDPSOCK_H */
> > > diff --git a/samples/bpf/xdpsock_kern.c b/samples/bpf/xdpsock_kern.c
> > > new file mode 100644
> > > index 0000000..a06177c
> > > --- /dev/null
> > > +++ b/samples/bpf/xdpsock_kern.c
> > > @@ -0,0 +1,24 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +#include <linux/bpf.h>
> > > +#include "bpf_helpers.h"
> > > +#include "xdpsock.h"
> > > +
> > > +/* This XDP program is only needed for the XDP_SHARED_UMEM mode.
> > > + * If you do not use this mode, libbpf can supply an XDP program for you.
> > > + */
> > > +
> > > +struct {
> > > +     __uint(type, BPF_MAP_TYPE_XSKMAP);
> > > +     __uint(max_entries, MAX_SOCKS);
> > > +     __uint(key_size, sizeof(int));
> > > +     __uint(value_size, sizeof(int));
> > > +} xsks_map SEC(".maps");
> > > +
> > > +static unsigned int rr;
> > > +
> > > +SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
> > > +{
> > > +     rr = (rr + 1) & (MAX_SOCKS - 1);
> > > +
> > > +     return bpf_redirect_map(&xsks_map, rr, XDP_DROP);
> > > +}
> > > diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> > > index 405c4e0..d3dba93 100644
> > > --- a/samples/bpf/xdpsock_user.c
> > > +++ b/samples/bpf/xdpsock_user.c
> > > @@ -29,6 +29,7 @@
> > >
> > >  #include "libbpf.h"
> > >  #include "xsk.h"
> > > +#include "xdpsock.h"
> > >  #include <bpf/bpf.h>
> > >
> > >  #ifndef SOL_XDP
> > > @@ -47,7 +48,6 @@
> > >  #define BATCH_SIZE 64
> > >
> > >  #define DEBUG_HEXDUMP 0
> > > -#define MAX_SOCKS 8
> > >
> > >  typedef __u64 u64;
> > >  typedef __u32 u32;
> > > @@ -75,7 +75,8 @@ static u32 opt_xdp_bind_flags;
> > >  static int opt_xsk_frame_size = XSK_UMEM__DEFAULT_FRAME_SIZE;
> > >  static int opt_timeout = 1000;
> > >  static bool opt_need_wakeup = true;
> > > -static __u32 prog_id;
> > > +static u32 opt_num_xsks = 1;
> > > +static u32 prog_id;
> > >
> > >  struct xsk_umem_info {
> > >       struct xsk_ring_prod fq;
> > > @@ -179,7 +180,7 @@ static void *poller(void *arg)
> > >
> > >  static void remove_xdp_program(void)
> > >  {
> > > -     __u32 curr_prog_id = 0;
> > > +     u32 curr_prog_id = 0;
> > >
> > >       if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
> > >               printf("bpf_get_link_xdp_id failed\n");
> > > @@ -196,11 +197,11 @@ static void remove_xdp_program(void)
> > >  static void int_exit(int sig)
> > >  {
> > >       struct xsk_umem *umem = xsks[0]->umem->umem;
> > > -
> > > -     (void)sig;
> > > +     int i;
> > >
> > >       dump_stats();
> > > -     xsk_socket__delete(xsks[0]->xsk);
> > > +     for (i = 0; i < num_socks; i++)
> > > +             xsk_socket__delete(xsks[i]->xsk);
> > >       (void)xsk_umem__delete(umem);
> > >       remove_xdp_program();
> > >
> > > @@ -290,8 +291,8 @@ static struct xsk_umem_info *xsk_configure_umem(void *buffer, u64 size)
> > >               .frame_headroom = XSK_UMEM__DEFAULT_FRAME_HEADROOM,
> > >               .flags = opt_umem_flags
> > >       };
> > > -
> > > -     int ret;
> > > +     int ret, i;
> > > +     u32 idx;
> > >
> > >       umem = calloc(1, sizeof(*umem));
> > >       if (!umem)
> > > @@ -303,6 +304,15 @@ static struct xsk_umem_info *xsk_configure_umem(void *buffer, u64 size)
> > >       if (ret)
> > >               exit_with_error(-ret);
> > >
> > > +     ret = xsk_ring_prod__reserve(&umem->fq,
> > > +                                  XSK_RING_PROD__DEFAULT_NUM_DESCS, &idx);
> > > +     if (ret != XSK_RING_PROD__DEFAULT_NUM_DESCS)
> > > +             exit_with_error(-ret);
> > > +     for (i = 0; i < XSK_RING_PROD__DEFAULT_NUM_DESCS; i++)
> > > +             *xsk_ring_prod__fill_addr(&umem->fq, idx++) =
> > > +                     i * opt_xsk_frame_size;
> > > +     xsk_ring_prod__submit(&umem->fq, XSK_RING_PROD__DEFAULT_NUM_DESCS);
> > > +
> > >       umem->buffer = buffer;
> > >       return umem;
> > >  }
> > > @@ -312,8 +322,6 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
> > >       struct xsk_socket_config cfg;
> > >       struct xsk_socket_info *xsk;
> > >       int ret;
> > > -     u32 idx;
> > > -     int i;
> > >
> > >       xsk = calloc(1, sizeof(*xsk));
> > >       if (!xsk)
> > > @@ -322,11 +330,15 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
> > >       xsk->umem = umem;
> > >       cfg.rx_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
> > >       cfg.tx_size = XSK_RING_PROD__DEFAULT_NUM_DESCS;
> > > -     cfg.libbpf_flags = 0;
> > > +     if (opt_num_xsks > 1)
> > > +             cfg.libbpf_flags = XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD;
> >
> > I think we can still load our own XDP program, and don't set
> > XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD.
> > So the xsk_setup_xdp_prog() will find the the loaded XDP program
> > and sets the xsk map.
> 
> So what you are saying is that you would like libbpf to be smarter and
> insert the sockets into the xskmap automatically? Doable in the simple

Isn't it already there?
xsk_setup_xdp_prog()
    xsk_lookup_bpf_maps() (it searches "xsks_maps")
    xsk_set_bpf_maps()
        insert socket into xskmap.

> case, but what if the XDP program has multiple xskmaps, or an xskmap
> with a different name? Seems complicated to do this in the general
> case. Or maybe I am just chicken to say the user has to load and
> manage his/her own XDP program when XDP_SHARED_UMEM is used :-).

Yes, if different name, then users have to program xskmap manually.

--William
> 
> > > +     else
> > > +             cfg.libbpf_flags = 0;
> > >       cfg.xdp_flags = opt_xdp_flags;
> > >       cfg.bind_flags = opt_xdp_bind_flags;
> >
> > Do we need to
> > cfg.bind_flags |= XDP_SHARED_UMEM?
> 
> It is set by libbpf automatically, so no need here.
> 
> > Thanks
> > William
> >
> > > -     ret = xsk_socket__create(&xsk->xsk, opt_if, opt_queue, umem->umem,
> > > -                              &xsk->rx, &xsk->tx, &cfg);
> > > +
> > > +     ret = xsk_socket__create(&xsk->xsk, opt_if, opt_queue,
> > > +                              umem->umem, &xsk->rx, &xsk->tx, &cfg);
> > >       if (ret)
> > >               exit_with_error(-ret);
> > >
> > > @@ -334,17 +346,6 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
> > >       if (ret)
> > >               exit_with_error(-ret);
> > >
> > > -     ret = xsk_ring_prod__reserve(&xsk->umem->fq,
> > > -                                  XSK_RING_PROD__DEFAULT_NUM_DESCS,
> > > -                                  &idx);
> > > -     if (ret != XSK_RING_PROD__DEFAULT_NUM_DESCS)
> > > -             exit_with_error(-ret);
> > > -     for (i = 0; i < XSK_RING_PROD__DEFAULT_NUM_DESCS; i++)
> > > -             *xsk_ring_prod__fill_addr(&xsk->umem->fq, idx++) =
> > > -                     i * opt_xsk_frame_size;
> > > -     xsk_ring_prod__submit(&xsk->umem->fq,
> > > -                           XSK_RING_PROD__DEFAULT_NUM_DESCS);
> > > -
> > >       return xsk;
> > >  }
> > >
> > > @@ -363,6 +364,7 @@ static struct option long_options[] = {
> > >       {"frame-size", required_argument, 0, 'f'},
> > >       {"no-need-wakeup", no_argument, 0, 'm'},
> > >       {"unaligned", no_argument, 0, 'u'},
> > > +     {"shared-umem", no_argument, 0, 'M'},
> > >       {0, 0, 0, 0}
> > >  };
> > >
> > > @@ -386,6 +388,7 @@ static void usage(const char *prog)
> > >               "  -m, --no-need-wakeup Turn off use of driver need wakeup flag.\n"
> > >               "  -f, --frame-size=n   Set the frame size (must be a power of two in aligned mode, default is %d).\n"
> > >               "  -u, --unaligned      Enable unaligned chunk placement\n"
> > > +             "  -M, --shared-umem    Enable XDP_SHARED_UMEM\n"
> > >               "\n";
> > >       fprintf(stderr, str, prog, XSK_UMEM__DEFAULT_FRAME_SIZE);
> > >       exit(EXIT_FAILURE);
> > > @@ -398,7 +401,7 @@ static void parse_command_line(int argc, char **argv)
> > >       opterr = 0;
> > >
> > >       for (;;) {
> > > -             c = getopt_long(argc, argv, "Frtli:q:psSNn:czf:mu",
> > > +             c = getopt_long(argc, argv, "Frtli:q:psSNn:czf:muM",
> > >                               long_options, &option_index);
> > >               if (c == -1)
> > >                       break;
> > > @@ -448,11 +451,14 @@ static void parse_command_line(int argc, char **argv)
> > >                       break;
> > >               case 'f':
> > >                       opt_xsk_frame_size = atoi(optarg);
> > > +                     break;
> > >               case 'm':
> > >                       opt_need_wakeup = false;
> > >                       opt_xdp_bind_flags &= ~XDP_USE_NEED_WAKEUP;
> > >                       break;
> > > -
> > > +             case 'M':
> > > +                     opt_num_xsks = MAX_SOCKS;
> > > +                     break;
> > >               default:
> > >                       usage(basename(argv[0]));
> > >               }
> > > @@ -586,11 +592,9 @@ static void rx_drop(struct xsk_socket_info *xsk, struct pollfd *fds)
> > >
> > >  static void rx_drop_all(void)
> > >  {
> > > -     struct pollfd fds[MAX_SOCKS + 1];
> > > +     struct pollfd fds[MAX_SOCKS] = {};
> > >       int i, ret;
> > >
> > > -     memset(fds, 0, sizeof(fds));
> > > -
> > >       for (i = 0; i < num_socks; i++) {
> > >               fds[i].fd = xsk_socket__fd(xsks[i]->xsk);
> > >               fds[i].events = POLLIN;
> > > @@ -633,11 +637,10 @@ static void tx_only(struct xsk_socket_info *xsk, u32 frame_nb)
> > >
> > >  static void tx_only_all(void)
> > >  {
> > > -     struct pollfd fds[MAX_SOCKS];
> > > +     struct pollfd fds[MAX_SOCKS] = {};
> > >       u32 frame_nb[MAX_SOCKS] = {};
> > >       int i, ret;
> > >
> > > -     memset(fds, 0, sizeof(fds));
> > >       for (i = 0; i < num_socks; i++) {
> > >               fds[0].fd = xsk_socket__fd(xsks[i]->xsk);
> > >               fds[0].events = POLLOUT;
> > > @@ -706,11 +709,9 @@ static void l2fwd(struct xsk_socket_info *xsk, struct pollfd *fds)
> > >
> > >  static void l2fwd_all(void)
> > >  {
> > > -     struct pollfd fds[MAX_SOCKS];
> > > +     struct pollfd fds[MAX_SOCKS] = {};
> > >       int i, ret;
> > >
> > > -     memset(fds, 0, sizeof(fds));
> > > -
> > >       for (i = 0; i < num_socks; i++) {
> > >               fds[i].fd = xsk_socket__fd(xsks[i]->xsk);
> > >               fds[i].events = POLLOUT | POLLIN;
> > > @@ -728,13 +729,65 @@ static void l2fwd_all(void)
> > >       }
> > >  }
> > >
> > > +static void load_xdp_program(char **argv, struct bpf_object **obj)
> > > +{
> > > +     struct bpf_prog_load_attr prog_load_attr = {
> > > +             .prog_type      = BPF_PROG_TYPE_XDP,
> > > +     };
> > > +     char xdp_filename[256];
> > > +     int prog_fd;
> > > +
> > > +     snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.o", argv[0]);
> > > +     prog_load_attr.file = xdp_filename;
> > > +
> > > +     if (bpf_prog_load_xattr(&prog_load_attr, obj, &prog_fd))
> > > +             exit(EXIT_FAILURE);
> > > +     if (prog_fd < 0) {
> > > +             fprintf(stderr, "ERROR: no program found: %s\n",
> > > +                     strerror(prog_fd));
> > > +             exit(EXIT_FAILURE);
> > > +     }
> > > +
> > > +     if (bpf_set_link_xdp_fd(opt_ifindex, prog_fd, opt_xdp_flags) < 0) {
> > > +             fprintf(stderr, "ERROR: link set xdp fd failed\n");
> > > +             exit(EXIT_FAILURE);
> > > +     }
> > > +}
> > > +
> > > +static void enter_xsks_into_map(struct bpf_object *obj)
> > > +{
> > > +     struct bpf_map *map;
> > > +     int i, xsks_map;
> > > +
> > > +     map = bpf_object__find_map_by_name(obj, "xsks_map");
> > > +     xsks_map = bpf_map__fd(map);
> > > +     if (xsks_map < 0) {
> > > +             fprintf(stderr, "ERROR: no xsks map found: %s\n",
> > > +                     strerror(xsks_map));
> > > +                     exit(EXIT_FAILURE);
> > > +     }
> > > +
> > > +     for (i = 0; i < num_socks; i++) {
> > > +             int fd = xsk_socket__fd(xsks[i]->xsk);
> > > +             int key, ret;
> > > +
> > > +             key = i;
> > > +             ret = bpf_map_update_elem(xsks_map, &key, &fd, 0);
> > > +             if (ret) {
> > > +                     fprintf(stderr, "ERROR: bpf_map_update_elem %d\n", i);
> > > +                     exit(EXIT_FAILURE);
> > > +             }
> > > +     }
> > > +}
> > > +
> > >  int main(int argc, char **argv)
> > >  {
> > >       struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
> > >       struct xsk_umem_info *umem;
> > > +     struct bpf_object *obj;
> > >       pthread_t pt;
> > > +     int i, ret;
> > >       void *bufs;
> > > -     int ret;
> > >
> > >       parse_command_line(argc, argv);
> > >
> > > @@ -744,6 +797,9 @@ int main(int argc, char **argv)
> > >               exit(EXIT_FAILURE);
> > >       }
> > >
> > > +     if (opt_num_xsks > 1)
> > > +             load_xdp_program(argv, &obj);
> > > +
> > >       /* Reserve memory for the umem. Use hugepages if unaligned chunk mode */
> > >       bufs = mmap(NULL, NUM_FRAMES * opt_xsk_frame_size,
> > >                   PROT_READ | PROT_WRITE,
> > > @@ -752,16 +808,17 @@ int main(int argc, char **argv)
> > >               printf("ERROR: mmap failed\n");
> > >               exit(EXIT_FAILURE);
> > >       }
> > > -       /* Create sockets... */
> > > +
> > > +     /* Create sockets... */
> > >       umem = xsk_configure_umem(bufs, NUM_FRAMES * opt_xsk_frame_size);
> > > -     xsks[num_socks++] = xsk_configure_socket(umem);
> > > +     for (i = 0; i < opt_num_xsks; i++)
> > > +             xsks[num_socks++] = xsk_configure_socket(umem);
> > >
> > > -     if (opt_bench == BENCH_TXONLY) {
> > > -             int i;
> > > +     for (i = 0; i < NUM_FRAMES; i++)
> > > +             gen_eth_frame(umem, i * opt_xsk_frame_size);
> > >
> > > -             for (i = 0; i < NUM_FRAMES; i++)
> > > -                     (void)gen_eth_frame(umem, i * opt_xsk_frame_size);
> > > -     }
> > > +     if (opt_num_xsks > 1 && opt_bench != BENCH_TXONLY)
> > > +             enter_xsks_into_map(obj);
> > >
> > >       signal(SIGINT, int_exit);
> > >       signal(SIGTERM, int_exit);
> > > --
> > > 2.7.4
> > >