[PATCH bpf-next 0/2] libbpf: add support for privileged/unprivileged control separation

[PATCH bpf-next 0/2] libbpf: add support for privileged/unprivileged control separation

[mariusz.dudek]

From: Mariusz Dudek <mariuszx.dudek@intel.com>

	This patch series adds support for separation of eBPF program
	load and xsk socket creation. In for example a Kubernetes
	environment you can have an AF_XDP CNI or daemonset that is 
	responsible for launching pods that execute an application 
	using AF_XDP sockets. It is desirable that the pod runs with
	as low privileges as possible, CAP_NET_RAW in this case, 
	and that all operations that require privileges are contained
	in the CNI or daemonset.
	
	In this case, you have to be able separate ePBF program load from
	xsk socket creation.

	Currently, this will not work with the xsk_socket__create APIs
	because you need to have CAP_NET_ADMIN privileges to load eBPF
	program and CAP_SYS_ADMIN privileges to create update xsk_bpf_maps.
	To be exact xsk_set_bpf_maps does not need those privileges but
	it takes the prog_fd and xsks_map_fd and those are known only to
	process that was loading eBPF program. The api bpf_prog_get_fd_by_id
	that looks up the fd of the prog using an prog_id and
	bpf_map_get_fd_by_id that looks for xsks_map_fd usinb map_id both
	requires CAP_SYS_ADMIN.

	With this patch, the pod can be run with CAP_NET_RAW capability
	only. In case your umem is larger or equal process limit for
	MEMLOCK you need either increase the limit or CAP_IPC_LOCK capability. 
	Without this patch in case of insufficient rights ENOPERM is
	returned by xsk_socket__create.

	To resolve this privileges issue two new APIs are introduced:
	- xsk_setup_xdp_prog - prepares bpf program if given and
	loads it on a selected network interface or loads the built in
	XDP program, if no XDP program is supplied. It can also return
	xsks_map_fd which is needed by unprivileged process to update
	xsks_map with AF_XDP socket "fd"
	- xsk_update_xskmap - inserts an AF_XDP socket into an xskmap for a
	particular xsk_socket

	Usage example:
	int xsk_setup_xdp_prog(int ifindex, struct bpf_prog_cfg *cfg,
			int *xsks_map_fd)

	if cfg == NULL, then the default program is loaded.

	Instead of NULL user can pass pointer to struct
	bpf_prog_cfg and provide own bpf program. 

	int xsk_update_xskmap(struct xsk_socket *xsk, int xsks_map_fd);

	Inserts AF_XDP socket "fd" into the xskmap.

	The first patch introduces the new APIs. The second patch provides
	a new sample applications working as control and modification to
	existing xdpsock application to work with less privileges.

	This patch set is based on bpf-next commit cb5dc5b062a9
	("Merge branch 'bpf: safeguard hashtab locking in NMI context')

Mariusz Dudek (2):
  libbpf: separate XDP program load with xsk socket creation
  samples/bpf: sample application for eBPF load and socket creation
    split

 samples/bpf/Makefile            |   4 +-
 samples/bpf/xdpsock.h           |   8 ++
 samples/bpf/xdpsock_ctrl_proc.c | 184 ++++++++++++++++++++++++++++++++
 samples/bpf/xdpsock_user.c      | 146 +++++++++++++++++++++++--
 tools/lib/bpf/libbpf.map        |   2 +
 tools/lib/bpf/xsk.c             | 157 ++++++++++++++++++++++-----
 tools/lib/bpf/xsk.h             |  13 +++
 7 files changed, 478 insertions(+), 36 deletions(-)
 create mode 100644 samples/bpf/xdpsock_ctrl_proc.c

-- 
2.20.1

[PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk socket creation

[mariusz.dudek]

From: Mariusz Dudek <mariuszx.dudek@intel.com>

        Add support for separation of eBPF program load and xsk socket
        creation.

        This is needed for use-case when you want to privide as little
        privileges as possible to the data plane application that will
        handle xsk socket creation and incoming traffic.

        With this patch the data entity container can be run with only
        CAP_NET_RAW capability to fulfill its purpose of creating xsk
        socket and handling packages. In case your umem is larger or
        equal process limit for MEMLOCK you need either increase the
        limit or CAP_IPC_LOCK capability.

        To resolve privileges issue two APIs are introduced:

        - xsk_setup_xdp_prog - prepares bpf program if given and
        loads it on a selected network interface or loads the built in
        XDP program, if no XDP program is supplied. It can also return
        xsks_map_fd which is needed by unprivileged process to update
        xsks_map with AF_XDP socket "fd"

        - xsk_update_xskmap - inserts an AF_XDP socket into an xskmap
	for a particular xsk_socket

Signed-off-by: Mariusz Dudek <mariuszx.dudek@intel.com>
---
 tools/lib/bpf/libbpf.map |   2 +
 tools/lib/bpf/xsk.c      | 157 ++++++++++++++++++++++++++++++++-------
 tools/lib/bpf/xsk.h      |  13 ++++
 3 files changed, 146 insertions(+), 26 deletions(-)

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 4ebfadf45b47..4b938de1ca39 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -336,4 +336,6 @@ LIBBPF_0.2.0 {
 		perf_buffer__epoll_fd;
 		perf_buffer__consume_buffer;
 		xsk_socket__create_shared;
+		xsk_setup_xdp_prog;
+		xsk_update_xskmap;
 } LIBBPF_0.1.0;
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index e3c98c007825..8c5219ceca45 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -351,13 +351,8 @@ int xsk_umem__create_v0_0_2(struct xsk_umem **umem_ptr, void *umem_area,
 COMPAT_VERSION(xsk_umem__create_v0_0_2, xsk_umem__create, LIBBPF_0.0.2)
 DEFAULT_VERSION(xsk_umem__create_v0_0_4, xsk_umem__create, LIBBPF_0.0.4)
 
-static int xsk_load_xdp_prog(struct xsk_socket *xsk)
+static int get_bpf_prog(struct bpf_prog_cfg *cfg_ptr, int xsks_map_fd)
 {
-	static const int log_buf_size = 16 * 1024;
-	struct xsk_ctx *ctx = xsk->ctx;
-	char log_buf[log_buf_size];
-	int err, prog_fd;
-
 	/* This is the C-program:
 	 * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
 	 * {
@@ -382,7 +377,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 		/* *(u32 *)(r10 - 4) = r2 */
 		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -4),
 		/* r1 = xskmap[] */
-		BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
+		BPF_LD_MAP_FD(BPF_REG_1, xsks_map_fd),
 		/* r3 = XDP_PASS */
 		BPF_MOV64_IMM(BPF_REG_3, 2),
 		/* call bpf_redirect_map */
@@ -394,7 +389,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 		/* r2 += -4 */
 		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
 		/* r1 = xskmap[] */
-		BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
+		BPF_LD_MAP_FD(BPF_REG_1, xsks_map_fd),
 		/* call bpf_map_lookup_elem */
 		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
 		/* r1 = r0 */
@@ -406,7 +401,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 		/* r2 = *(u32 *)(r10 - 4) */
 		BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_10, -4),
 		/* r1 = xskmap[] */
-		BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
+		BPF_LD_MAP_FD(BPF_REG_1, xsks_map_fd),
 		/* r3 = 0 */
 		BPF_MOV64_IMM(BPF_REG_3, 0),
 		/* call bpf_redirect_map */
@@ -414,17 +409,42 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 		/* The jumps are to this instruction */
 		BPF_EXIT_INSN(),
 	};
-	size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
 
-	prog_fd = bpf_load_program(BPF_PROG_TYPE_XDP, prog, insns_cnt,
-				   "LGPL-2.1 or BSD-2-Clause", 0, log_buf,
+	cfg_ptr->prog = malloc(sizeof(prog));
+	if (!cfg_ptr->prog)
+		return -ENOMEM;
+	memcpy(cfg_ptr->prog, prog, sizeof(prog));
+	cfg_ptr->license = "LGPL-2.1 or BSD-2-Clause";
+	cfg_ptr->insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
+
+	return 0;
+}
+
+static int xsk_load_xdp_prog(struct xsk_socket *xsk, struct bpf_prog_cfg *user_cfg)
+{
+	static const int log_buf_size = 16 * 1024;
+	struct xsk_ctx *ctx = xsk->ctx;
+	char log_buf[log_buf_size];
+	struct bpf_prog_cfg cfg;
+	int err, prog_fd;
+
+	if (user_cfg && user_cfg->insns_cnt) {
+		cfg = *user_cfg;
+	} else {
+		err = get_bpf_prog(&cfg, ctx->xsks_map_fd);
+		if (err)
+			return err;
+	}
+
+	prog_fd = bpf_load_program(BPF_PROG_TYPE_XDP, cfg.prog, cfg.insns_cnt,
+				   cfg.license, 0, log_buf,
 				   log_buf_size);
 	if (prog_fd < 0) {
 		pr_warn("BPF log buffer:\n%s", log_buf);
 		return prog_fd;
 	}
 
-	err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd,
+	err = bpf_set_link_xdp_fd(ctx->ifindex, prog_fd,
 				  xsk->config.xdp_flags);
 	if (err) {
 		close(prog_fd);
@@ -566,8 +586,43 @@ static int xsk_set_bpf_maps(struct xsk_socket *xsk)
 				   &xsk->fd, 0);
 }
 
-static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
+static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk)
+{
+	char ifname[IFNAMSIZ];
+	struct xsk_ctx *ctx;
+	char *interface;
+	int res = -1;
+
+	ctx = calloc(1, sizeof(*ctx));
+	if (!ctx)
+		goto error_ctx;
+
+	interface = if_indextoname(ifindex, &ifname[0]);
+	if (!interface) {
+		res = -errno;
+		goto error_ifindex;
+	}
+
+	ctx->ifindex = ifindex;
+	strncpy(ctx->ifname, ifname, IFNAMSIZ - 1);
+	ctx->ifname[IFNAMSIZ - 1] = 0;
+
+	xsk->ctx = ctx;
+
+	return 0;
+
+error_ifindex:
+	free(ctx);
+error_ctx:
+	return res;
+}
+
+static int __xsk_setup_xdp_prog(struct xsk_socket *_xdp,
+				struct bpf_prog_cfg *cfg,
+				bool force_set_map,
+				int *xsks_map_fd)
 {
+	struct xsk_socket *xsk = _xdp;
 	struct xsk_ctx *ctx = xsk->ctx;
 	__u32 prog_id = 0;
 	int err;
@@ -578,14 +633,17 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
 		return err;
 
 	if (!prog_id) {
-		err = xsk_create_bpf_maps(xsk);
-		if (err)
-			return err;
+		if (!cfg || !cfg->insns_cnt) {
+			err = xsk_create_bpf_maps(xsk);
+			if (err)
+				return err;
+		} else {
+			ctx->xsks_map_fd = cfg->xsks_map_fd;
+		}
 
-		err = xsk_load_xdp_prog(xsk);
+		err = xsk_load_xdp_prog(xsk, cfg);
 		if (err) {
-			xsk_delete_bpf_maps(xsk);
-			return err;
+			goto err_load_xdp_prog;
 		}
 	} else {
 		ctx->prog_fd = bpf_prog_get_fd_by_id(prog_id);
@@ -598,15 +656,29 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
 		}
 	}
 
-	if (xsk->rx)
+	if (xsk->rx || force_set_map) {
 		err = xsk_set_bpf_maps(xsk);
-	if (err) {
-		xsk_delete_bpf_maps(xsk);
-		close(ctx->prog_fd);
-		return err;
+		if (err) {
+			if (!prog_id) {
+				goto err_set_bpf_maps;
+			} else {
+				close(ctx->prog_fd);
+				return err;
+			}
+		}
 	}
+	if (xsks_map_fd)
+		*xsks_map_fd = ctx->xsks_map_fd;
 
 	return 0;
+
+err_set_bpf_maps:
+	close(ctx->prog_fd);
+	bpf_set_link_xdp_fd(ctx->ifindex, -1, 0);
+err_load_xdp_prog:
+	xsk_delete_bpf_maps(xsk);
+
+	return err;
 }
 
 static struct xsk_ctx *xsk_get_ctx(struct xsk_umem *umem, int ifindex,
@@ -689,6 +761,39 @@ static struct xsk_ctx *xsk_create_ctx(struct xsk_socket *xsk,
 	return ctx;
 }
 
+static void xsk_destroy_xsk_struct(struct xsk_socket *xsk)
+{
+	free(xsk->ctx);
+	free(xsk);
+}
+
+int xsk_update_xskmap(struct xsk_socket *xsk, int fd)
+{
+	xsk->ctx->xsks_map_fd = fd;
+	return xsk_set_bpf_maps(xsk);
+}
+
+int xsk_setup_xdp_prog(int ifindex, struct bpf_prog_cfg *cfg,
+		       int *xsks_map_fd)
+{
+	struct xsk_socket *xsk;
+	int res = -1;
+
+	xsk = calloc(1, sizeof(*xsk));
+	if (!xsk)
+		return res;
+
+	res = xsk_create_xsk_struct(ifindex, xsk);
+	if (res)
+		return -EINVAL;
+
+	res = __xsk_setup_xdp_prog(xsk, cfg, false, xsks_map_fd);
+
+	xsk_destroy_xsk_struct(xsk);
+
+	return res;
+}
+
 int xsk_socket__create_shared(struct xsk_socket **xsk_ptr,
 			      const char *ifname,
 			      __u32 queue_id, struct xsk_umem *umem,
@@ -838,7 +943,7 @@ int xsk_socket__create_shared(struct xsk_socket **xsk_ptr,
 	ctx->prog_fd = -1;
 
 	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
-		err = xsk_setup_xdp_prog(xsk);
+		err = __xsk_setup_xdp_prog(xsk, NULL, false, NULL);
 		if (err)
 			goto out_mmap_tx;
 	}
diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
index 1069c46364ff..c42b91935d3c 100644
--- a/tools/lib/bpf/xsk.h
+++ b/tools/lib/bpf/xsk.h
@@ -201,6 +201,19 @@ struct xsk_umem_config {
 	__u32 flags;
 };
 
+struct bpf_prog_cfg {
+	struct bpf_insn *prog;
+	const char *license;
+	size_t insns_cnt;
+	int xsks_map_fd;
+};
+
+LIBBPF_API int xsk_setup_xdp_prog(int ifindex,
+				  struct bpf_prog_cfg *cfg,
+				  int *xsks_map_fd);
+LIBBPF_API int xsk_update_xskmap(struct xsk_socket *xsk,
+				 int xsks_map_fd);
+
 /* Flags for the libbpf_flags field. */
 #define XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD (1 << 0)
 
-- 
2.20.1

[PATCH bpf-next 2/2] samples/bpf: sample application for eBPF load and socket creation split

[mariusz.dudek]

From: Mariusz Dudek <mariuszx.dudek@intel.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@intel.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..c841aca59a96
--- /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)
+		return -errno;
+
+	sock = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (sock < 0) {
+		fprintf(stderr, "Opening socket stream failed: %s", strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	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, NULL, &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 1149e94ca32f..c3ca5304fce4 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]));
+	}
 }
 
 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_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

Re: [PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk socket creation

[Andrii Nakryiko]

On Wed, Nov 4, 2020 at 1:47 AM <mariusz.dudek@gmail.com> wrote:
>
> From: Mariusz Dudek <mariuszx.dudek@intel.com>
>
>         Add support for separation of eBPF program load and xsk socket
>         creation.
>
>         This is needed for use-case when you want to privide as little
>         privileges as possible to the data plane application that will
>         handle xsk socket creation and incoming traffic.
>
>         With this patch the data entity container can be run with only
>         CAP_NET_RAW capability to fulfill its purpose of creating xsk
>         socket and handling packages. In case your umem is larger or
>         equal process limit for MEMLOCK you need either increase the
>         limit or CAP_IPC_LOCK capability.
>
>         To resolve privileges issue two APIs are introduced:
>
>         - xsk_setup_xdp_prog - prepares bpf program if given and
>         loads it on a selected network interface or loads the built in
>         XDP program, if no XDP program is supplied. It can also return
>         xsks_map_fd which is needed by unprivileged process to update
>         xsks_map with AF_XDP socket "fd"
>
>         - xsk_update_xskmap - inserts an AF_XDP socket into an xskmap
>         for a particular xsk_socket
>

Your commit message seems to be heavily shifted right...


> Signed-off-by: Mariusz Dudek <mariuszx.dudek@intel.com>
> ---
>  tools/lib/bpf/libbpf.map |   2 +
>  tools/lib/bpf/xsk.c      | 157 ++++++++++++++++++++++++++++++++-------
>  tools/lib/bpf/xsk.h      |  13 ++++
>  3 files changed, 146 insertions(+), 26 deletions(-)
>

[...]

> diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> index 1069c46364ff..c42b91935d3c 100644
> --- a/tools/lib/bpf/xsk.h
> +++ b/tools/lib/bpf/xsk.h
> @@ -201,6 +201,19 @@ struct xsk_umem_config {
>         __u32 flags;
>  };
>
> +struct bpf_prog_cfg {
> +       struct bpf_insn *prog;
> +       const char *license;
> +       size_t insns_cnt;
> +       int xsks_map_fd;
> +};

This config will have problems with backward/forward compatibility.
Please check how xxx_opts are done and use them for extensible options
structs.


> +
> +LIBBPF_API int xsk_setup_xdp_prog(int ifindex,
> +                                 struct bpf_prog_cfg *cfg,
> +                                 int *xsks_map_fd);
> +LIBBPF_API int xsk_update_xskmap(struct xsk_socket *xsk,
> +                                int xsks_map_fd);

this should be called xsk_socket__update_map? BTW, what's xskmap? Is
that a special BPF map type?

> +
>  /* Flags for the libbpf_flags field. */
>  #define XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD (1 << 0)
>
> --
> 2.20.1
>

Re: [PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk socket creation

[Mariusz Dudek]

On Wed, Nov 4, 2020 at 10:07 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Wed, Nov 4, 2020 at 1:47 AM <mariusz.dudek@gmail.com> wrote:
> >
> > From: Mariusz Dudek <mariuszx.dudek@intel.com>
> >
> >         Add support for separation of eBPF program load and xsk socket
> >         creation.
> >
> >         This is needed for use-case when you want to privide as little
> >         privileges as possible to the data plane application that will
> >         handle xsk socket creation and incoming traffic.
> >
> >         With this patch the data entity container can be run with only
> >         CAP_NET_RAW capability to fulfill its purpose of creating xsk
> >         socket and handling packages. In case your umem is larger or
> >         equal process limit for MEMLOCK you need either increase the
> >         limit or CAP_IPC_LOCK capability.
> >
> >         To resolve privileges issue two APIs are introduced:
> >
> >         - xsk_setup_xdp_prog - prepares bpf program if given and
> >         loads it on a selected network interface or loads the built in
> >         XDP program, if no XDP program is supplied. It can also return
> >         xsks_map_fd which is needed by unprivileged process to update
> >         xsks_map with AF_XDP socket "fd"
> >
> >         - xsk_update_xskmap - inserts an AF_XDP socket into an xskmap
> >         for a particular xsk_socket
> >
>
> Your commit message seems to be heavily shifted right...
>
Will be fixed
>
> > Signed-off-by: Mariusz Dudek <mariuszx.dudek@intel.com>
> > ---
> >  tools/lib/bpf/libbpf.map |   2 +
> >  tools/lib/bpf/xsk.c      | 157 ++++++++++++++++++++++++++++++++-------
> >  tools/lib/bpf/xsk.h      |  13 ++++
> >  3 files changed, 146 insertions(+), 26 deletions(-)
> >
>
> [...]
>
> > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> > index 1069c46364ff..c42b91935d3c 100644
> > --- a/tools/lib/bpf/xsk.h
> > +++ b/tools/lib/bpf/xsk.h
> > @@ -201,6 +201,19 @@ struct xsk_umem_config {
> >         __u32 flags;
> >  };
> >
> > +struct bpf_prog_cfg {
> > +       struct bpf_insn *prog;
> > +       const char *license;
> > +       size_t insns_cnt;
> > +       int xsks_map_fd;
> > +};
>
> This config will have problems with backward/forward compatibility.
> Please check how xxx_opts are done and use them for extensible options
> structs.
>
I will add struct size as first parameter and #define for __last_field
to be inline with xxx_opts
>
> > +
> > +LIBBPF_API int xsk_setup_xdp_prog(int ifindex,
> > +                                 struct bpf_prog_cfg *cfg,
> > +                                 int *xsks_map_fd);
> > +LIBBPF_API int xsk_update_xskmap(struct xsk_socket *xsk,
> > +                                int xsks_map_fd);
>
> this should be called xsk_socket__update_map? BTW, what's xskmap? Is
> that a special BPF map type?
>
I will change the API name as you suggested. XSKMAP is a special
BPF_MAP_TYPE_XSKMAP.
It defines how packets are being distributed from an XDP program to the XSKs.
> > +
> >  /* Flags for the libbpf_flags field. */
> >  #define XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD (1 << 0)
> >
> > --
> > 2.20.1
> >