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Date: Tue, 19 Jan 2021 16:36:52 +0100
From: Björn Töpel <bjorn.topel@...il.com>
To: ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
bpf@...r.kernel.org
Cc: Björn Töpel <bjorn.topel@...el.com>,
magnus.karlsson@...el.com, maciej.fijalkowski@...el.com,
kuba@...nel.org, jonathan.lemon@...il.com, maximmi@...dia.com,
davem@...emloft.net, hawk@...nel.org, john.fastabend@...il.com,
ciara.loftus@...el.com, weqaar.a.janjua@...el.com,
Marek Majtyka <alardam@...il.com>
Subject: [PATCH bpf-next 5/8] libbpf, xsk: select AF_XDP BPF program based on kernel version
From: Björn Töpel <bjorn.topel@...el.com>
Add detection for kernel version, and adapt the BPF program based on
kernel support. This way, users will get the best possible performance
from the BPF program.
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
Signed-off-by: Marek Majtyka <alardam@...il.com>
---
tools/lib/bpf/libbpf.c | 2 +-
tools/lib/bpf/libbpf_internal.h | 2 ++
tools/lib/bpf/libbpf_probes.c | 16 -------------
tools/lib/bpf/xsk.c | 41 ++++++++++++++++++++++++++++++---
4 files changed, 41 insertions(+), 20 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2abbc3800568..6a53adf14a9c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -693,7 +693,7 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
return 0;
}
-static __u32 get_kernel_version(void)
+__u32 get_kernel_version(void)
{
__u32 major, minor, patch;
struct utsname info;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 969d0ac592ba..dafb780e2dd2 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -349,4 +349,6 @@ struct bpf_core_relo {
enum bpf_core_relo_kind kind;
};
+__u32 get_kernel_version(void);
+
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index ecaae2927ab8..aae0231371d0 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -48,22 +48,6 @@ static int get_vendor_id(int ifindex)
return strtol(buf, NULL, 0);
}
-static int get_kernel_version(void)
-{
- int version, subversion, patchlevel;
- struct utsname utsn;
-
- /* Return 0 on failure, and attempt to probe with empty kversion */
- if (uname(&utsn))
- return 0;
-
- if (sscanf(utsn.release, "%d.%d.%d",
- &version, &subversion, &patchlevel) != 3)
- return 0;
-
- return (version << 16) + (subversion << 8) + patchlevel;
-}
-
static void
probe_load(enum bpf_prog_type prog_type, const struct bpf_insn *insns,
size_t insns_cnt, char *buf, size_t buf_len, __u32 ifindex)
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index e3e41ceeb1bc..c8642c6cb5d6 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -23,6 +23,7 @@
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sockios.h>
+#include <linux/version.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
@@ -46,6 +47,11 @@
#define PF_XDP AF_XDP
#endif
+enum xsk_prog {
+ XSK_PROG_FALLBACK,
+ XSK_PROG_REDIRECT_FLAGS,
+};
+
struct xsk_umem {
struct xsk_ring_prod *fill_save;
struct xsk_ring_cons *comp_save;
@@ -351,6 +357,13 @@ 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 enum xsk_prog get_xsk_prog(void)
+{
+ __u32 kver = get_kernel_version();
+
+ return kver < KERNEL_VERSION(5, 3, 0) ? XSK_PROG_FALLBACK : XSK_PROG_REDIRECT_FLAGS;
+}
+
static int xsk_load_xdp_prog(struct xsk_socket *xsk)
{
static const int log_buf_size = 16 * 1024;
@@ -358,7 +371,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
char log_buf[log_buf_size];
int err, prog_fd;
- /* This is the C-program:
+ /* This is the fallback C-program:
* SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
* {
* int ret, index = ctx->rx_queue_index;
@@ -414,9 +427,31 @@ 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,
+ /* This is the post-5.3 kernel C-program:
+ * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
+ * {
+ * return bpf_redirect_map(&xsks_map, ctx->rx_queue_index, XDP_PASS);
+ * }
+ */
+ struct bpf_insn prog_redirect_flags[] = {
+ /* r2 = *(u32 *)(r1 + 16) */
+ BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 16),
+ /* r1 = xskmap[] */
+ BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
+ /* r3 = XDP_PASS */
+ BPF_MOV64_IMM(BPF_REG_3, 2),
+ /* call bpf_redirect_map */
+ BPF_EMIT_CALL(BPF_FUNC_redirect_map),
+ BPF_EXIT_INSN(),
+ };
+ size_t insns_cnt[] = {sizeof(prog) / sizeof(struct bpf_insn),
+ sizeof(prog_redirect_flags) / sizeof(struct bpf_insn),
+ };
+ struct bpf_insn *progs[] = {prog, prog_redirect_flags};
+ enum xsk_prog option = get_xsk_prog();
+
+ prog_fd = bpf_load_program(BPF_PROG_TYPE_XDP, progs[option], insns_cnt[option],
"LGPL-2.1 or BSD-2-Clause", 0, log_buf,
log_buf_size);
if (prog_fd < 0) {
--
2.27.0
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