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Date: Thu, 26 Nov 2020 09:31:48 +0100
From: Mariusz Dudek <mariusz.dudek@...il.com>
To: Magnus Karlsson <magnus.karlsson@...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 1/2] libbpf: separate XDP program load with
xsk socket creation
On Wed, Nov 25, 2020 at 3:30 PM Magnus Karlsson
<magnus.karlsson@...il.com> wrote:
>
> On Wed, Nov 18, 2020 at 9:34 AM <mariusz.dudek@...il.com> wrote:
> >
> > From: Mariusz Dudek <mariuszx.dudek@...el.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 - loads the built in XDP program. It can
> > also return xsks_map_fd which is needed by unprivileged process
> > to update xsks_map with AF_XDP socket "fd"
> >
> > - xsk_socket__update_xskmap - inserts an AF_XDP socket into an xskmap
> > for a particular xsk_socket
> >
> > Signed-off-by: Mariusz Dudek <mariuszx.dudek@...el.com>
> > ---
> > tools/lib/bpf/libbpf.map | 2 +
> > tools/lib/bpf/xsk.c | 97 ++++++++++++++++++++++++++++++++++++----
> > tools/lib/bpf/xsk.h | 5 +++
> > 3 files changed, 95 insertions(+), 9 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> > index 29ff4807b909..d939d5ac092e 100644
> > --- a/tools/lib/bpf/libbpf.map
> > +++ b/tools/lib/bpf/libbpf.map
> > @@ -345,4 +345,6 @@ LIBBPF_0.3.0 {
> > btf__parse_split;
> > btf__new_empty_split;
> > btf__new_split;
> > + xsk_setup_xdp_prog;
> > + xsk_socket__update_xskmap;
> > } LIBBPF_0.2.0;
> > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> > index 9bc537d0b92d..e16f920d2ef9 100644
> > --- a/tools/lib/bpf/xsk.c
> > +++ b/tools/lib/bpf/xsk.c
> > @@ -566,8 +566,42 @@ 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;
>
> No need to set it to -1 anymore, due to the below.
Will fix this
>
> > +
> > + ctx = calloc(1, sizeof(*ctx));
> > + if (!ctx)
> > + goto error_ctx;
>
> return an -ENOMEM here directly.
-ENOMEM will be returned
>
> > +
> > + 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:
>
> And you can get rid of this label.
I will get rid of both labels as I can return either -ENOMEM or -errno
from both places directly
>
> > + return res;
> > +}
> > +
> > +static int __xsk_setup_xdp_prog(struct xsk_socket *_xdp,
> > + bool force_set_map,
>
> force_set_map always seems to be false now. Correct? If it is, then it
> is not needed anymore. What was the original use case of this boolean?
>
force_set_map was used before for setting xsk bpf maps, but after code
change it is no longer needed. I will remove it.
> > + int *xsks_map_fd)
> > +{
> > + struct xsk_socket *xsk = _xdp;
> > struct xsk_ctx *ctx = xsk->ctx;
> > __u32 prog_id = 0;
> > int err;
> > @@ -584,8 +618,7 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> >
> > err = xsk_load_xdp_prog(xsk);
> > 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 +631,29 @@ 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 +736,38 @@ 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_socket__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, 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;
>
> Here you can now return the error from the function, i.e. return res,
> as we returned -ENOMEM in that function. You are however leaking the
> xsk struct you just allocated in case of error. Needs to be
> deallocated.
>
xsk struct deallocated. -ENOMEM returned in case calloc fails.
> > +
> > + res = __xsk_setup_xdp_prog(xsk, 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 +917,7 @@ 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, false, NULL);
> > if (err)
> > goto out_mmap_tx;
> > }
> > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> > index 1069c46364ff..5b74c17ed3d4 100644
> > --- a/tools/lib/bpf/xsk.h
> > +++ b/tools/lib/bpf/xsk.h
> > @@ -201,6 +201,11 @@ struct xsk_umem_config {
> > __u32 flags;
> > };
> >
> > +LIBBPF_API int xsk_setup_xdp_prog(int ifindex,
> > + int *xsks_map_fd);
> > +LIBBPF_API int xsk_socket__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
> >
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