Date:   Wed, 25 Nov 2020 15:42:02 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Mariusz Dudek <mariusz.dudek@...il.com>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Network Development <netdev@...r.kernel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        bpf <bpf@...r.kernel.org>,
        Mariusz Dudek <mariuszx.dudek@...el.com>
Subject: Re: [PATCH v3 bpf-next 2/2] samples/bpf: sample application for eBPF
 load and socket creation split

On Wed, Nov 18, 2020 at 9:34 AM <mariusz.dudek@...il.com> wrote:
>
> From: Mariusz Dudek <mariuszx.dudek@...el.com>
>
> Introduce a sample program to demonstrate the control and data
> plane split. For the control plane part a new program called
> xdpsock_ctrl_proc is introduced. For the data plane part, some code
> was added to xdpsock_user.c to act as the data plane entity.
>
> Application xdpsock_ctrl_proc works as control entity with sudo
> privileges (CAP_SYS_ADMIN and CAP_NET_ADMIN are sufficient) and the
> extended xdpsock as data plane entity with CAP_NET_RAW capability
> only.
>
> Usage example:
>
> sudo ./samples/bpf/xdpsock_ctrl_proc -i <interface>
>
> sudo ./samples/bpf/xdpsock -i <interface> -q <queue_id>
>         -n <interval> -N -l -R
>
> Signed-off-by: Mariusz Dudek <mariuszx.dudek@...el.com>
> ---
>  samples/bpf/Makefile            |   4 +-
>  samples/bpf/xdpsock.h           |   8 ++
>  samples/bpf/xdpsock_ctrl_proc.c | 184 ++++++++++++++++++++++++++++++++
>  samples/bpf/xdpsock_user.c      | 146 +++++++++++++++++++++++--
>  4 files changed, 332 insertions(+), 10 deletions(-)
>  create mode 100644 samples/bpf/xdpsock_ctrl_proc.c
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index aeebf5d12f32..8fb8be1c0144 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -48,6 +48,7 @@ tprogs-y += syscall_tp
>  tprogs-y += cpustat
>  tprogs-y += xdp_adjust_tail
>  tprogs-y += xdpsock
> +tprogs-y += xdpsock_ctrl_proc
>  tprogs-y += xsk_fwd
>  tprogs-y += xdp_fwd
>  tprogs-y += task_fd_query
> @@ -105,6 +106,7 @@ syscall_tp-objs := syscall_tp_user.o
>  cpustat-objs := cpustat_user.o
>  xdp_adjust_tail-objs := xdp_adjust_tail_user.o
>  xdpsock-objs := xdpsock_user.o
> +xdpsock_ctrl_proc-objs := xdpsock_ctrl_proc.o
>  xsk_fwd-objs := xsk_fwd.o
>  xdp_fwd-objs := xdp_fwd_user.o
>  task_fd_query-objs := bpf_load.o task_fd_query_user.o $(TRACE_HELPERS)
> @@ -204,7 +206,7 @@ TPROGLDLIBS_tracex4         += -lrt
>  TPROGLDLIBS_trace_output       += -lrt
>  TPROGLDLIBS_map_perf_test      += -lrt
>  TPROGLDLIBS_test_overhead      += -lrt
> -TPROGLDLIBS_xdpsock            += -pthread
> +TPROGLDLIBS_xdpsock            += -pthread -lcap
>  TPROGLDLIBS_xsk_fwd            += -pthread
>
>  # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
> diff --git a/samples/bpf/xdpsock.h b/samples/bpf/xdpsock.h
> index b7eca15c78cc..fd70cce60712 100644
> --- a/samples/bpf/xdpsock.h
> +++ b/samples/bpf/xdpsock.h
> @@ -8,4 +8,12 @@
>
>  #define MAX_SOCKS 4
>
> +#define SOCKET_NAME "sock_cal_bpf_fd"
> +#define MAX_NUM_OF_CLIENTS 10
> +
> +#define CLOSE_CONN  1
> +
> +typedef __u64 u64;
> +typedef __u32 u32;
> +
>  #endif /* XDPSOCK_H */
> diff --git a/samples/bpf/xdpsock_ctrl_proc.c b/samples/bpf/xdpsock_ctrl_proc.c
> new file mode 100644
> index 000000000000..9d9e65e5552d
> --- /dev/null
> +++ b/samples/bpf/xdpsock_ctrl_proc.c
> @@ -0,0 +1,184 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright(c) 2017 - 2018 Intel Corporation. */
> +
> +#include <errno.h>
> +#include <getopt.h>
> +#include <libgen.h>
> +#include <net/if.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/socket.h>
> +#include <sys/un.h>
> +#include <unistd.h>
> +
> +#include <bpf/bpf.h>
> +#include <bpf/xsk.h>
> +#include "xdpsock.h"
> +
> +static const char *opt_if = "";
> +
> +static struct option long_options[] = {
> +       {"interface", required_argument, 0, 'i'},
> +       {0, 0, 0, 0}
> +};
> +
> +static void usage(const char *prog)
> +{
> +       const char *str =
> +               "  Usage: %s [OPTIONS]\n"
> +               "  Options:\n"
> +               "  -i, --interface=n    Run on interface n\n"
> +               "\n";
> +       fprintf(stderr, "%s\n", str);
> +
> +       exit(0);
> +}
> +
> +static void parse_command_line(int argc, char **argv)
> +{
> +       int option_index, c;
> +
> +       opterr = 0;
> +
> +       for (;;) {
> +               c = getopt_long(argc, argv, "i:",
> +                               long_options, &option_index);
> +               if (c == -1)
> +                       break;
> +
> +               switch (c) {
> +               case 'i':
> +                       opt_if = optarg;
> +                       break;
> +               default:
> +                       usage(basename(argv[0]));
> +               }
> +       }
> +}
> +
> +static int send_xsks_map_fd(int sock, int fd)
> +{
> +       char cmsgbuf[CMSG_SPACE(sizeof(int))];
> +       struct msghdr msg;
> +       struct iovec iov;
> +       int value = 0;
> +
> +       if (fd == -1) {
> +               fprintf(stderr, "Incorrect fd = %d\n", fd);
> +               return -1;
> +       }
> +       iov.iov_base = &value;
> +       iov.iov_len = sizeof(int);
> +
> +       msg.msg_name = NULL;
> +       msg.msg_namelen = 0;
> +       msg.msg_iov = &iov;
> +       msg.msg_iovlen = 1;
> +       msg.msg_flags = 0;
> +       msg.msg_control = cmsgbuf;
> +       msg.msg_controllen = CMSG_LEN(sizeof(int));
> +
> +       struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
> +
> +       cmsg->cmsg_level = SOL_SOCKET;
> +       cmsg->cmsg_type = SCM_RIGHTS;
> +       cmsg->cmsg_len = CMSG_LEN(sizeof(int));
> +
> +       *(int *)CMSG_DATA(cmsg) = fd;
> +       int ret = sendmsg(sock, &msg, 0);
> +
> +       if (ret == -1) {
> +               fprintf(stderr, "Sendmsg failed with %s", strerror(errno));
> +               return -errno;
> +       }
> +
> +       return ret;
> +}
> +
> +int
> +main(int argc, char **argv)
> +{
> +       struct sockaddr_un server;
> +       int listening = 1;
> +       int rval, msgsock;
> +       int ifindex = 0;
> +       int flag = 1;
> +       int cmd = 0;
> +       int sock;
> +       int err;
> +       int xsks_map_fd;
> +
> +       parse_command_line(argc, argv);
> +
> +       ifindex = if_nametoindex(opt_if);
> +       if (ifindex == 0)

How about printing an error message here too? Interface name not
valid, or something like that.

> +               return -errno;
> +
> +       sock = socket(AF_UNIX, SOCK_STREAM, 0);
> +       if (sock < 0) {
> +               fprintf(stderr, "Opening socket stream failed: %s", strerror(errno));
> +               exit(EXIT_FAILURE);

You mix returning error numbers and using exit(EXIT_FAILURE). I say
stick to returning an error, return err.

> +       }
> +
> +       server.sun_family = AF_UNIX;
> +       strcpy(server.sun_path, SOCKET_NAME);
> +
> +       setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(int));
> +
> +       if (bind(sock, (struct sockaddr *)&server, sizeof(struct sockaddr_un))) {
> +               fprintf(stderr, "Binding to socket stream failed: %s", strerror(errno));
> +               exit(EXIT_FAILURE);
> +       }
> +
> +       listen(sock, MAX_NUM_OF_CLIENTS);
> +
> +       err = xsk_setup_xdp_prog(ifindex, &xsks_map_fd);
> +       if (err) {
> +               fprintf(stderr, "Setup of xdp program failed\n");
> +               goto close_sock;
> +       }
> +
> +       while (listening) {
> +               msgsock = accept(sock, 0, 0);
> +               if (msgsock == -1) {
> +                       fprintf(stderr, "Error accepting connection: %s", strerror(errno));
> +                       err = -errno;
> +                       goto close_sock;
> +               }
> +               err = send_xsks_map_fd(msgsock, xsks_map_fd);
> +               if (err <= 0) {
> +                       fprintf(stderr, "Error %d sending xsks_map_fd\n", err);
> +                       goto cleanup;
> +               }
> +               do {
> +                       rval = read(msgsock, &cmd, sizeof(int));
> +                       if (rval < 0) {
> +                               fprintf(stderr, "Error reading stream message");
> +                       } else {
> +                               if (cmd != CLOSE_CONN)
> +                                       fprintf(stderr, "Recv unknown cmd = %d\n", cmd);
> +                               listening = 0;
> +                               break;
> +                       }
> +               } while (rval > 0);
> +       }
> +       close(msgsock);
> +       close(sock);
> +       unlink(SOCKET_NAME);
> +
> +       /* Unset fd for given ifindex */
> +       err = bpf_set_link_xdp_fd(ifindex, -1, 0);
> +       if (err) {
> +               fprintf(stderr, "Error when unsetting bpf prog_fd for ifindex(%d)\n", ifindex);
> +               return err;
> +       }
> +
> +       return 0;
> +
> +cleanup:
> +       close(msgsock);
> +close_sock:
> +       close(sock);
> +       unlink(SOCKET_NAME);
> +       return err;
> +}
> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> index 2567f0db5aca..589344fd1eb5 100644
> --- a/samples/bpf/xdpsock_user.c
> +++ b/samples/bpf/xdpsock_user.c
> @@ -24,10 +24,12 @@
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <string.h>
> +#include <sys/capability.h>
>  #include <sys/mman.h>
>  #include <sys/resource.h>
>  #include <sys/socket.h>
>  #include <sys/types.h>
> +#include <sys/un.h>
>  #include <time.h>
>  #include <unistd.h>
>
> @@ -95,6 +97,7 @@ static int opt_timeout = 1000;
>  static bool opt_need_wakeup = true;
>  static u32 opt_num_xsks = 1;
>  static u32 prog_id;
> +static bool opt_reduced_cap;
>
>  struct xsk_ring_stats {
>         unsigned long rx_npkts;
> @@ -153,6 +156,7 @@ struct xsk_socket_info {
>
>  static int num_socks;
>  struct xsk_socket_info *xsks[MAX_SOCKS];
> +int sock;
>
>  static unsigned long get_nsecs(void)
>  {
> @@ -460,6 +464,7 @@ static void *poller(void *arg)
>  static void remove_xdp_program(void)
>  {
>         u32 curr_prog_id = 0;
> +       int cmd = CLOSE_CONN;
>
>         if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
>                 printf("bpf_get_link_xdp_id failed\n");
> @@ -471,6 +476,13 @@ static void remove_xdp_program(void)
>                 printf("couldn't find a prog id on a given interface\n");
>         else
>                 printf("program on interface changed, not removing\n");
> +
> +       if (opt_reduced_cap) {
> +               if (write(sock, &cmd, sizeof(int)) < 0) {
> +                       fprintf(stderr, "Error writing into stream socket: %s", strerror(errno));
> +                       exit(EXIT_FAILURE);
> +               }
> +       }
>  }
>
>  static void int_exit(int sig)
> @@ -853,7 +865,7 @@ 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;
> -       if (opt_num_xsks > 1)
> +       if (opt_num_xsks > 1 || opt_reduced_cap)
>                 cfg.libbpf_flags = XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD;
>         else
>                 cfg.libbpf_flags = 0;
> @@ -911,6 +923,7 @@ static struct option long_options[] = {
>         {"quiet", no_argument, 0, 'Q'},
>         {"app-stats", no_argument, 0, 'a'},
>         {"irq-string", no_argument, 0, 'I'},
> +       {"reduce-cap", no_argument, 0, 'R'},
>         {0, 0, 0, 0}
>  };
>
> @@ -933,7 +946,7 @@ 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"
> +               "  -M, --shared-umem    Enable XDP_SHARED_UMEM (cannot be used with -R)\n"
>                 "  -F, --force          Force loading the XDP prog\n"
>                 "  -d, --duration=n     Duration in secs to run command.\n"
>                 "                       Default: forever.\n"
> @@ -949,6 +962,7 @@ static void usage(const char *prog)
>                 "  -Q, --quiet          Do not display any stats.\n"
>                 "  -a, --app-stats      Display application (syscall) statistics.\n"
>                 "  -I, --irq-string     Display driver interrupt statistics for interface associated with irq-string.\n"
> +               "  -R, --reduce-cap     Use reduced capabilities (cannot be used with -M)\n"
>                 "\n";
>         fprintf(stderr, str, prog, XSK_UMEM__DEFAULT_FRAME_SIZE,
>                 opt_batch_size, MIN_PKT_SIZE, MIN_PKT_SIZE,
> @@ -964,7 +978,7 @@ static void parse_command_line(int argc, char **argv)
>         opterr = 0;
>
>         for (;;) {
> -               c = getopt_long(argc, argv, "Frtli:q:pSNn:czf:muMd:b:C:s:P:xQaI:",
> +               c = getopt_long(argc, argv, "Frtli:q:pSNn:czf:muMd:b:C:s:P:xQaI:R",
>                                 long_options, &option_index);
>                 if (c == -1)
>                         break;
> @@ -1063,6 +1077,9 @@ static void parse_command_line(int argc, char **argv)
>                                 usage(basename(argv[0]));
>                         }
>
> +                       break;
> +               case 'R':
> +                       opt_reduced_cap = true;
>                         break;
>                 default:
>                         usage(basename(argv[0]));
> @@ -1085,6 +1102,11 @@ static void parse_command_line(int argc, char **argv)
>                         opt_xsk_frame_size);
>                 usage(basename(argv[0]));
>         }
> +
> +       if (opt_reduced_cap && opt_num_xsks > 1) {
> +               fprintf(stderr, "ERROR: -M and -R cannot be used together\n");
> +               usage(basename(argv[0]));
> +       }

There is nothing in principle that hinders this, but it would be a
much more complicated example, so this restriction is fine.

>  }
>
>  static void kick_tx(struct xsk_socket_info *xsk)
> @@ -1461,26 +1483,117 @@ static void enter_xsks_into_map(struct bpf_object *obj)
>         }
>  }
>
> +static int recv_xsks_map_fd_from_ctrl_node(int sock, int *_fd)
> +{
> +       char cms[CMSG_SPACE(sizeof(int))];
> +       struct cmsghdr *cmsg;
> +       struct msghdr msg;
> +       struct iovec iov;
> +       int value;
> +       int len;
> +
> +       iov.iov_base = &value;
> +       iov.iov_len = sizeof(int);
> +
> +       msg.msg_name = 0;
> +       msg.msg_namelen = 0;
> +       msg.msg_iov = &iov;
> +       msg.msg_iovlen = 1;
> +       msg.msg_flags = 0;
> +       msg.msg_control = (caddr_t)cms;
> +       msg.msg_controllen = sizeof(cms);
> +
> +       len = recvmsg(sock, &msg, 0);
> +
> +       if (len < 0) {
> +               fprintf(stderr, "Recvmsg failed length incorrect.\n");
> +               return -EINVAL;
> +       }
> +
> +       if (len == 0) {
> +               fprintf(stderr, "Recvmsg failed no data\n");
> +               return -EINVAL;
> +       }
> +
> +       cmsg = CMSG_FIRSTHDR(&msg);
> +       *_fd = *(int *)CMSG_DATA(cmsg);
> +
> +       return 0;
> +}
> +
> +static int
> +recv_xsks_map_fd(int *xsks_map_fd)
> +{
> +       struct sockaddr_un server;
> +       int err;
> +
> +       sock = socket(AF_UNIX, SOCK_STREAM, 0);
> +       if (sock < 0) {
> +               fprintf(stderr, "Error opening socket stream: %s", strerror(errno));
> +               return errno;
> +       }
> +
> +       server.sun_family = AF_UNIX;
> +       strcpy(server.sun_path, SOCKET_NAME);
> +
> +       if (connect(sock, (struct sockaddr *)&server, sizeof(struct sockaddr_un)) < 0) {
> +               close(sock);
> +               fprintf(stderr, "Error connecting stream socket: %s", strerror(errno));
> +               return errno;
> +       }
> +
> +       err = recv_xsks_map_fd_from_ctrl_node(sock, xsks_map_fd);
> +       if (err) {
> +               fprintf(stderr, "Error %d recieving fd\n", err);
> +               return err;
> +       }
> +       return 0;
> +}
> +
>  int main(int argc, char **argv)
>  {
> +       struct __user_cap_header_struct hdr = { _LINUX_CAPABILITY_VERSION_3, 0 };
> +       struct __user_cap_data_struct data[2] = { { 0 } };
>         struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
>         bool rx = false, tx = false;
>         struct xsk_umem_info *umem;
>         struct bpf_object *obj;
> +       int xsks_map_fd = 0;
>         pthread_t pt;
>         int i, ret;
>         void *bufs;
>
>         parse_command_line(argc, argv);
>
> -       if (setrlimit(RLIMIT_MEMLOCK, &r)) {
> -               fprintf(stderr, "ERROR: setrlimit(RLIMIT_MEMLOCK) \"%s\"\n",
> -                       strerror(errno));
> -               exit(EXIT_FAILURE);
> +       if (opt_reduced_cap) {
> +               if (capget(&hdr, data)  < 0)
> +                       fprintf(stderr, "Error getting capabilities\n");
> +
> +               data->effective &= CAP_TO_MASK(CAP_NET_RAW);
> +               data->permitted &= CAP_TO_MASK(CAP_NET_RAW);
> +
> +               if (capset(&hdr, data) < 0)
> +                       fprintf(stderr, "Setting capabilities failed\n");
> +
> +               if (capget(&hdr, data)  < 0) {
> +                       fprintf(stderr, "Error getting capabilities\n");
> +               } else {
> +                       fprintf(stderr, "Capabilities EFF %x Caps INH %x Caps Per %x\n",
> +                               data[0].effective, data[0].inheritable, data[0].permitted);
> +                       fprintf(stderr, "Capabilities EFF %x Caps INH %x Caps Per %x\n",
> +                               data[1].effective, data[1].inheritable, data[1].permitted);
> +               }
> +       } else {
> +               if (setrlimit(RLIMIT_MEMLOCK, &r)) {
> +                       fprintf(stderr, "ERROR: setrlimit(RLIMIT_MEMLOCK) \"%s\"\n",
> +                               strerror(errno));
> +                       exit(EXIT_FAILURE);
> +               }
> +
> +               if (opt_num_xsks > 1)
> +                       load_xdp_program(argv, &obj);
>         }
>
> -       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,
> @@ -1512,6 +1625,21 @@ int main(int argc, char **argv)
>         if (opt_num_xsks > 1 && opt_bench != BENCH_TXONLY)
>                 enter_xsks_into_map(obj);
>
> +       if (opt_reduced_cap) {
> +               ret = recv_xsks_map_fd(&xsks_map_fd);
> +               if (ret) {
> +                       fprintf(stderr, "Error %d receiving xsks_map_fd\n", ret);
> +                       exit_with_error(ret);
> +               }
> +               if (xsks[0]->xsk) {
> +                       ret = xsk_socket__update_xskmap(xsks[0]->xsk, xsks_map_fd);
> +                       if (ret) {
> +                               fprintf(stderr, "Update of BPF map failed(%d)\n", ret);
> +                               exit_with_error(ret);
> +                       }
> +               }
> +       }
> +
>         signal(SIGINT, int_exit);
>         signal(SIGTERM, int_exit);
>         signal(SIGABRT, int_exit);
> --
> 2.20.1
>

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