On Tue, May 05, 2020 at 01:27:29PM -0700, Stanislav Fomichev wrote:
> We want to have a tighter control on what ports we bind to in
> the BPF_CGROUP_INET{4,6}_CONNECT hooks even if it means
> connect() becomes slightly more expensive. The expensive part
> comes from the fact that we now need to call inet_csk_get_port()
> that verifies that the port is not used and allocates an entry
> in the hash table for it.
>
> Since we can't rely on "snum || !bind_address_no_port" to prevent
> us from calling POST_BIND hook anymore, let's add another bind flag
> to indicate that the call site is BPF program.
>
> v2:
> * Update documentation (Andrey Ignatov)
> * Pass BIND_FORCE_ADDRESS_NO_PORT conditionally (Andrey Ignatov)
>
> Cc: Andrey Ignatov <r...@fb.com>
> Signed-off-by: Stanislav Fomichev <s...@google.com>
> ---
> include/net/inet_common.h | 2 +
> include/uapi/linux/bpf.h | 9 +-
> net/core/filter.c | 18 ++-
> net/ipv4/af_inet.c | 10 +-
> net/ipv6/af_inet6.c | 12 +-
> tools/include/uapi/linux/bpf.h | 9 +-
> .../bpf/prog_tests/connect_force_port.c | 104 ++++++++++++++++++
> .../selftests/bpf/progs/connect_force_port4.c | 28 +++++
> .../selftests/bpf/progs/connect_force_port6.c | 28 +++++
> 9 files changed, 192 insertions(+), 28 deletions(-)
> create mode 100644
> tools/testing/selftests/bpf/prog_tests/connect_force_port.c
> create mode 100644 tools/testing/selftests/bpf/progs/connect_force_port4.c
> create mode 100644 tools/testing/selftests/bpf/progs/connect_force_port6.c
>
> diff --git a/include/net/inet_common.h b/include/net/inet_common.h
> index c38f4f7d660a..cb2818862919 100644
> --- a/include/net/inet_common.h
> +++ b/include/net/inet_common.h
> @@ -39,6 +39,8 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr,
> int addr_len);
> #define BIND_FORCE_ADDRESS_NO_PORT (1 << 0)
> /* Grab and release socket lock. */
> #define BIND_WITH_LOCK (1 << 1)
> +/* Called from BPF program. */
> +#define BIND_FROM_BPF (1 << 2)
> int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
> u32 flags);
> int inet_getname(struct socket *sock, struct sockaddr *uaddr,
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index b3643e27e264..14b5518a3d5b 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -1994,10 +1994,11 @@ union bpf_attr {
> *
> * This helper works for IPv4 and IPv6, TCP and UDP sockets. The
> * domain (*addr*\ **->sa_family**) must be **AF_INET** (or
> - * **AF_INET6**). Looking for a free port to bind to can be
> - * expensive, therefore binding to port is not permitted by the
> - * helper: *addr*\ **->sin_port** (or **sin6_port**, respectively)
> - * must be set to zero.
> + * **AF_INET6**). It's advised to pass zero port (**sin_port**
> + * or **sin6_port**) which triggers IP_BIND_ADDRESS_NO_PORT-like
> + * behavior and lets the kernel reuse the same source port
Reading "zero port" and "the same source port" together is confusing.
> + * as long as 4-tuple is unique. Passing non-zero port might
> + * lead to degraded performance.
Is the "degraded performance" also true for UDP?
> * Return
> * 0 on success, or a negative error in case of failure.
> *
[ ... ]
> diff --git a/tools/testing/selftests/bpf/prog_tests/connect_force_port.c
> b/tools/testing/selftests/bpf/prog_tests/connect_force_port.c
> new file mode 100644
> index 000000000000..97104e6410b6
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/connect_force_port.c
> @@ -0,0 +1,104 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include "cgroup_helpers.h"
> +#include "network_helpers.h"
> +
> +static int verify_port(int family, int fd, int expected)
> +{
> + struct sockaddr_storage addr;
> + socklen_t len = sizeof(addr);
> + __u16 port;
> +
> +
> + if (getsockname(fd, (struct sockaddr *)&addr, &len)) {
> + log_err("Failed to get server addr");
> + return -1;
> + }
> +
> + if (family == AF_INET)
> + port = ((struct sockaddr_in *)&addr)->sin_port;
> + else
> + port = ((struct sockaddr_in6 *)&addr)->sin6_port;
> +
> + if (ntohs(port) != expected) {
> + log_err("Unexpected port %d, expected %d", ntohs(port),
> + expected);
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> +static int run_test(int cgroup_fd, int server_fd, int family)
> +{
> + struct bpf_prog_load_attr attr = {
> + .prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
> + };
> + struct bpf_object *obj;
> + int expected_port;
> + int prog_fd;
> + int err;
> + int fd;
> +
> + if (family == AF_INET) {
> + attr.file = "./connect_force_port4.o";
> + attr.expected_attach_type = BPF_CGROUP_INET4_CONNECT;
> + expected_port = 22222;
> + } else {
> + attr.file = "./connect_force_port6.o";
> + attr.expected_attach_type = BPF_CGROUP_INET6_CONNECT;
> + expected_port = 22223;
> + }
> +
> + err = bpf_prog_load_xattr(&attr, &obj, &prog_fd);
> + if (err) {
> + log_err("Failed to load BPF object");
> + return -1;
> + }
> +
> + err = bpf_prog_attach(prog_fd, cgroup_fd, attr.expected_attach_type,
> + 0);
> + if (err) {
> + log_err("Failed to attach BPF program");
> + goto close_bpf_object;
> + }
> +
> + fd = connect_to_fd(family, server_fd);
> + if (fd < 0) {
> + err = -1;
> + goto close_bpf_object;
> + }
> +
> + err = verify_port(family, fd, expected_port);
> +
> + close(fd);
> +
> +close_bpf_object:
> + bpf_object__close(obj);
> + return err;
> +}
> +
> +void test_connect_force_port(void)
> +{
> + int server_fd, cgroup_fd;
> +
> + cgroup_fd = test__join_cgroup("/connect_force_port");
> + if (CHECK_FAIL(cgroup_fd < 0))
> + return;
> +
> + server_fd = start_server_thread(AF_INET);
> + if (CHECK_FAIL(server_fd < 0))
> + goto close_cgroup_fd;
> + CHECK_FAIL(run_test(cgroup_fd, server_fd, AF_INET));
> + stop_server_thread(server_fd);
> +
> + server_fd = start_server_thread(AF_INET6);
> + if (CHECK_FAIL(server_fd < 0))
> + goto close_cgroup_fd;
> + CHECK_FAIL(run_test(cgroup_fd, server_fd, AF_INET6));
> + stop_server_thread(server_fd);
Thanks for testing both v6 and v4.
The UDP path should be tested also.
