[ovs-dev] [PATCH v3 4/4] bpf: Add reference XDP program implementation for netdev-offload-xdp

Toshiaki Makita toshiaki.makita1 at gmail.com
Mon Jun 29 15:30:33 UTC 2020


This adds a reference program, flowtable_afxdp.o, which can be used to
offload flows to XDP through netdev-offload-xdp.
The program can be compiled with --enable-bpf switch.

Signed-off-by: Toshiaki Makita <toshiaki.makita1 at gmail.com>
---
 Makefile.am           |   9 +-
 acinclude.m4          |  57 ++++
 bpf/.gitignore        |   4 +
 bpf/Makefile.am       |  61 +++++
 bpf/bpf_compiler.h    |  25 ++
 bpf/bpf_miniflow.h    | 179 +++++++++++++
 bpf/bpf_netlink.h     |  62 +++++
 bpf/bpf_workaround.h  |  28 ++
 bpf/flowtable_afxdp.c | 585 ++++++++++++++++++++++++++++++++++++++++++
 configure.ac          |   2 +
 10 files changed, 1010 insertions(+), 2 deletions(-)
 create mode 100644 bpf/.gitignore
 create mode 100644 bpf/Makefile.am
 create mode 100644 bpf/bpf_compiler.h
 create mode 100644 bpf/bpf_miniflow.h
 create mode 100644 bpf/bpf_netlink.h
 create mode 100644 bpf/bpf_workaround.h
 create mode 100644 bpf/flowtable_afxdp.c

diff --git a/Makefile.am b/Makefile.am
index b279303d1..f18bfefde 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -8,6 +8,9 @@
 AUTOMAKE_OPTIONS = foreign subdir-objects
 ACLOCAL_AMFLAGS = -I m4
 SUBDIRS = datapath
+if HAVE_BPF
+SUBDIRS += bpf
+endif
 
 AM_CPPFLAGS = $(SSL_CFLAGS)
 AM_LDFLAGS = $(SSL_LDFLAGS)
@@ -198,7 +201,9 @@ ALL_LOCAL += dist-hook-git
 dist-hook-git: distfiles
 	@if test -e $(srcdir)/.git && (git --version) >/dev/null 2>&1; then \
 	  (cd datapath && $(MAKE) distfiles); \
-	  (cat distfiles; sed 's|^|datapath/|' datapath/distfiles) | \
+	  (cd bpf && $(MAKE) distfiles); \
+	  (cat distfiles; sed 's|^|datapath/|' datapath/distfiles; \
+	   sed 's|^|bpf/|' bpf/distfiles) | \
 	    LC_ALL=C sort -u > all-distfiles; \
 	  (cd $(srcdir) && git ls-files) | grep -v '\.gitignore$$' | \
 	    grep -v '\.gitattributes$$' | \
@@ -234,7 +239,7 @@ config-h-check:
 	@cd $(srcdir); \
 	if test -e .git && (git --version) >/dev/null 2>&1 && \
 	  git --no-pager grep -L '#include <config\.h>' `git ls-files | grep '\.c$$' | \
-	    grep -vE '^datapath|^lib/sflow|^third-party|^datapath-windows|^python'`; \
+	    grep -vE '^datapath|^lib/sflow|^third-party|^datapath-windows|^python|^bpf'`; \
 	then \
 	  echo "See above for list of violations of the rule that"; \
 	  echo "every C source file must #include <config.h>."; \
diff --git a/acinclude.m4 b/acinclude.m4
index 8847b8145..8d481eb98 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -301,6 +301,63 @@ AC_DEFUN([OVS_CHECK_LINUX_AF_XDP], [
   AM_CONDITIONAL([HAVE_AF_XDP], test "$AF_XDP_ENABLE" = true)
 ])
 
+dnl OVS_CHECK_LINUX_BPF
+dnl
+dnl Check both llvm and libbpf support
+AC_DEFUN([OVS_CHECK_LINUX_BPF], [
+  AC_ARG_ENABLE([bpf],
+                [AC_HELP_STRING([--enable-bpf],
+                                [Compile reference eBPF programs for XDP])],
+                [], [enable_bpf=no])
+  AC_MSG_CHECKING([whether BPF is enabled])
+  if test "$enable_bpf" != yes; then
+    AC_MSG_RESULT([no])
+    BPF_ENABLE=false
+  else
+    AC_MSG_RESULT([yes])
+    BPF_ENABLE=true
+
+    AC_CHECK_PROG(CLANG_CHECK, clang, yes)
+    AS_IF([test X"$CLANG_CHECK" != X"yes"],
+      [AC_MSG_ERROR([unable to find clang to compile BPF program])])
+
+    AC_CHECK_PROG(LLC_CHECK, llc, yes)
+    AS_IF([test X"$LLC_CHECK" != X"yes"],
+      [AC_MSG_ERROR([unable to find llc to compile BPF program])])
+
+    AC_CHECK_HEADER([bpf/bpf_helpers.h], [],
+      [AC_MSG_ERROR([unable to find bpf/bpf_helpers.h to compile BPF program])],
+      [#include <linux/types.h>])
+
+    AC_CHECK_HEADER([linux/bpf.h], [],
+      [AC_MSG_ERROR([unable to find linux/bpf.h to compile BPF program])])
+
+    AC_MSG_CHECKING([for LLVM bpf target support])
+    if llc -march=bpf -mattr=help >/dev/null 2>&1; then
+      AC_MSG_RESULT([yes])
+    else
+      AC_MSG_RESULT([no])
+      AC_MSG_ERROR([LLVM does not support bpf target])
+    fi
+
+    AC_MSG_CHECKING([for BTF DATASEC support])
+    AC_LANG_CONFTEST(
+      [AC_LANG_SOURCE([__attribute__((section("_x"), used)) int x;])])
+    if clang -g -O2 -S -target bpf -emit-llvm -c conftest.c -o conftest.ll && \
+       llc -march=bpf -filetype=obj -o conftest.o conftest.ll && \
+       readelf -p.BTF conftest.o 2>/dev/null | grep -q -w _x; then
+      AC_MSG_RESULT([yes])
+    else
+      AC_MSG_RESULT([no])
+      AC_MSG_ERROR([LLVM does not support BTF DATASEC])
+    fi
+
+    AC_DEFINE([HAVE_BPF], [1],
+              [Define to 1 if BPF compilation is available and enabled.])
+  fi
+  AM_CONDITIONAL([HAVE_BPF], test "$BPF_ENABLE" = true)
+])
+
 dnl OVS_CHECK_DPDK
 dnl
 dnl Configure DPDK source tree
diff --git a/bpf/.gitignore b/bpf/.gitignore
new file mode 100644
index 000000000..ab0f2d9e4
--- /dev/null
+++ b/bpf/.gitignore
@@ -0,0 +1,4 @@
+*.ll
+/distfiles
+/Makefile
+/Makefile.in
diff --git a/bpf/Makefile.am b/bpf/Makefile.am
new file mode 100644
index 000000000..0335e5fcc
--- /dev/null
+++ b/bpf/Makefile.am
@@ -0,0 +1,61 @@
+AUTOMAKE_OPTIONS = foreign
+
+EXTRA_DIST = flowtable_afxdp.c bpf_compiler.h bpf_miniflow.h bpf_netlink.h \
+	bpf_workaround.h
+
+# The following is based on commands for the Automake "distdir" target.
+distfiles: Makefile
+	@srcdirstrip=`echo "$(srcdir)" | sed 's/[].[^$$\\*]/\\\\&/g'`; \
+	topsrcdirstrip=`echo "$(top_srcdir)" | sed 's/[].[^$$\\*]/\\\\&/g'`; \
+	list='$(DISTFILES)'; \
+	for file in $$list; do echo $$file; done | \
+	  sed -e "s|^$$srcdirstrip/||;t" \
+	      -e "s|^$$topsrcdirstrip/|$(top_builddir)/|;t" | \
+	  LC_ALL=C sort -u > $@
+CLEANFILES = distfiles
+
+CLANG ?= clang
+LLC ?= llc
+
+AM_CPPFLAGS = -I $(top_srcdir)/include
+AM_CPPFLAGS += -I $(top_builddir)/include
+AM_CPPFLAGS += -I $(top_srcdir)/lib
+AM_CPPFLAGS += -I $(top_builddir)/lib
+
+AM_CFLAGS = -Wall
+AM_CFLAGS += -Wextra
+AM_CFLAGS += -Wno-sign-compare
+AM_CFLAGS += -Wformat -Wformat-security
+AM_CFLAGS += -Wswitch-enum
+AM_CFLAGS += -Wunused-parameter
+AM_CFLAGS += -Wbad-function-cast
+AM_CFLAGS += -Wcast-align
+AM_CFLAGS += -Wstrict-prototypes
+AM_CFLAGS += -Wold-style-definition
+AM_CFLAGS += -Wmissing-field-initializers
+AM_CFLAGS += -fno-strict-aliasing
+AM_CFLAGS += -Wswitch-bool
+AM_CFLAGS += -Wlogical-not-parentheses
+AM_CFLAGS += -Wsizeof-array-argument
+AM_CFLAGS += -Wshift-negative-value
+AM_CFLAGS += -Wshadow
+AM_CFLAGS += -Wcast-align
+AM_CFLAGS += -Wno-unused-value
+AM_CFLAGS += -Wno-compare-distinct-pointer-types
+AM_CFLAGS += -g
+AM_CFLAGS += -O2
+
+SUFFIXES = .ll
+%.ll: %.c
+	$(CLANG) $(AM_CPPFLAGS) $(AM_CFLAGS) -S \
+		-target bpf -emit-llvm -c $< -o $@
+CLEANFILES += *.ll
+
+%.o: %.ll
+	$(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ $<
+CLEANFILES += *.o
+
+flowtable_afxdp.o: flowtable_afxdp.c bpf_compiler.h bpf_miniflow.h \
+	bpf_netlink.h bpf_workaround.h
+
+all-local: flowtable_afxdp.o
diff --git a/bpf/bpf_compiler.h b/bpf/bpf_compiler.h
new file mode 100644
index 000000000..1d6223390
--- /dev/null
+++ b/bpf/bpf_compiler.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2020 NTT Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BPF_COMPILER_H
+#define BPF_COMPILER_H
+
+/* Hint for compiler: make register value unknown to compiler and prevent
+ * following code, e.g. bound check, from being omitted */
+#define bpf_compiler_reg_barrier(val) __asm__ __volatile__("":"+r"(val));
+
+#endif /* bpf_compiler.h */
+
diff --git a/bpf/bpf_miniflow.h b/bpf/bpf_miniflow.h
new file mode 100644
index 000000000..090a9c7be
--- /dev/null
+++ b/bpf/bpf_miniflow.h
@@ -0,0 +1,179 @@
+/*
+ * Copyright (c) 2020 NTT Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BPF_MINIFLOW_H
+#define BPF_MINIFLOW_H 1
+
+#include "flow.h"
+
+struct bpf_mf_ctx {
+    struct flowmap map;
+    uint64_t *data;
+};
+
+static inline void
+miniflow_set_maps(struct bpf_mf_ctx *ctx, size_t ofs, size_t n_words)
+{
+    flowmap_set(&ctx->map, ofs, n_words);
+}
+
+static inline void
+miniflow_set_map(struct bpf_mf_ctx *ctx, size_t ofs)
+{
+    flowmap_set(&ctx->map, ofs, 1);
+}
+
+static inline void
+miniflow_push_uint8_(struct bpf_mf_ctx *ctx, size_t ofs, uint8_t value)
+{
+    size_t ofs8 = ofs % 8;
+
+    if (ofs8 == 0) {
+        miniflow_set_map(ctx, ofs / 8);
+    }
+    *((uint8_t *)ctx->data + ofs8) = value;
+    if (ofs8 == 7) {
+        ctx->data++;
+    }
+}
+
+static inline void
+miniflow_push_uint16_(struct bpf_mf_ctx *ctx, size_t ofs, uint16_t value)
+{
+    size_t ofs8 = ofs % 8;
+
+    if (ofs8 == 0) {
+        miniflow_set_map(ctx, ofs / 8);
+        *(uint16_t *)ctx->data = value;
+    } else if (ofs8 == 2) {
+        *((uint16_t *)ctx->data + 1) = value;
+    } else if (ofs8 == 4) {
+        *((uint16_t *)ctx->data + 2) = value;
+    } else if (ofs8 == 6) {
+        *((uint16_t *)ctx->data + 3) = value;
+        ctx->data++;
+    }
+}
+
+static inline void
+miniflow_push_uint32_(struct bpf_mf_ctx *ctx, size_t ofs, uint32_t value)
+{
+    size_t ofs8 = ofs % 8;
+
+    if (ofs8 == 0) {
+        miniflow_set_map(ctx, ofs / 8);
+        *(uint32_t *)ctx->data = value;
+    } else if (ofs8 == 4) {
+        *((uint32_t *)ctx->data + 1) = value;
+        ctx->data++;
+    }
+}
+
+static inline void
+ether_addr_copy(struct eth_addr *dst, const struct eth_addr *src)
+{
+    ovs_be16 *a = dst->be16;
+    const ovs_be16 *b = src->be16;
+
+    a[0] = b[0];
+    a[1] = b[1];
+    a[2] = b[2];
+}
+
+/* 'valuep' is 16-aligned */
+/* data must start 64-aligned and must be followed by other data or padding */
+static inline void
+miniflow_push_macs_(struct bpf_mf_ctx *ctx, size_t ofs,
+                    const struct eth_addr *valuep)
+{
+    miniflow_set_maps(ctx, ofs / 8, 2);
+    ether_addr_copy((struct eth_addr *)ctx->data, valuep);
+    ether_addr_copy((struct eth_addr *)ctx->data + 1, valuep + 1);
+    ctx->data++; /* First word only. */
+}
+
+/* data must start 64-aligned and must be followed by other data */
+static inline void
+miniflow_pad_from_64_(struct bpf_mf_ctx *ctx, size_t ofs)
+{
+    size_t ofs8 = ofs % 8;
+    size_t ofs4 = ofs % 4;
+    size_t ofs2 = ofs % 2;
+    void *cdata = ctx->data;
+
+    miniflow_set_map(ctx, ofs / 8);
+
+    if (ofs8 >= 4) {
+        *(uint32_t *)cdata = 0;
+        cdata += 4;
+    }
+    if (ofs4 >= 2) {
+        *(uint16_t *)cdata = 0;
+        cdata += 2;
+    }
+    if (ofs2 == 1) {
+        *(uint8_t *)cdata = 0;
+    }
+}
+
+static inline void
+miniflow_pad_to_64_(struct bpf_mf_ctx *ctx, size_t ofs)
+{
+    size_t ofs8 = ofs % 8;
+    size_t ofs4 = ofs % 4;
+    size_t ofs2 = ofs % 2;
+    void *cdata = ctx->data;
+
+    cdata += ofs8;
+    if (ofs2 == 1) {
+        *(uint8_t *)cdata = 0;
+        cdata++;
+    }
+    if (ofs4 <= 2) {
+        *(uint16_t *)cdata = 0;
+        cdata += 2;
+    }
+    if (ofs8 <= 4) {
+        *(uint32_t *)cdata = 0;
+    }
+    ctx->data++;
+}
+
+#define miniflow_push_uint8(CTX, FIELD, VALUE)                       \
+    miniflow_push_uint8_(CTX, offsetof(struct flow, FIELD), VALUE)
+
+#define miniflow_push_be16_(CTX, OFS, VALUE)                         \
+    miniflow_push_uint16_(CTX, OFS, (OVS_FORCE uint16_t)VALUE)
+
+#define miniflow_push_be16(CTX, FIELD, VALUE)                        \
+    miniflow_push_be16_(CTX, offsetof(struct flow, FIELD), VALUE)    \
+
+#define miniflow_push_be32_(CTX, OFS, VALUE)                         \
+    miniflow_push_uint32_(CTX, OFS, (OVS_FORCE uint32_t)VALUE)
+
+#define miniflow_push_be32(CTX, FIELD, VALUE)                        \
+    miniflow_push_be32_(CTX, offsetof(struct flow, FIELD), VALUE)    \
+
+#define miniflow_push_macs(CTX, FIELD, VALUEP)                       \
+    miniflow_push_macs_(CTX, offsetof(struct flow, FIELD), VALUEP)
+
+#define miniflow_pad_from_64(CTX, FIELD)                             \
+    miniflow_pad_from_64_(CTX, offsetof(struct flow, FIELD))
+
+#define miniflow_pad_to_64(CTX, FIELD)                               \
+    miniflow_pad_to_64_(CTX, OFFSETOFEND(struct flow, FIELD))
+
+#endif /* bpf_miniflow.h */
diff --git a/bpf/bpf_netlink.h b/bpf/bpf_netlink.h
new file mode 100644
index 000000000..6a10e2d3d
--- /dev/null
+++ b/bpf/bpf_netlink.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2020 NTT Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BPF_NETLINK_H
+#define BPF_NETLINK_H 1
+
+#include "bpf_compiler.h"
+#include "netlink.h"
+
+static inline int
+bpf_nl_attr_type(const struct nlattr *nla)
+{
+    return nla->nla_type & NLA_TYPE_MASK;
+}
+
+static inline const void *
+bpf_nl_attr_get(const struct nlattr *nla)
+{
+    return nla + 1;
+}
+
+static inline size_t
+bpf_map_nl_attr_next_offset(void *start, size_t offset, size_t max_len)
+{
+    const struct nlattr *nla;
+
+    /* Use offset (scalar) to cap the bounds of nla pointer address (map_value)
+     * because map_value's min/max cannot be set by cond jmp ops in verifier */
+    bpf_compiler_reg_barrier(offset);
+    if (offset > max_len - sizeof *nla) {
+        return max_len;
+    }
+
+    nla = (const struct nlattr *)(start + offset);
+    offset += NLA_ALIGN(nla->nla_len);
+    if (offset >= max_len) {
+        return max_len;
+    }
+
+    return offset;
+}
+
+/* NOTE: (IDX) < (MAX_ATTRS) is mandatory for verifier */
+#define BPF_MAP_NL_ATTR_FOR_EACH(OFF, ATTRS, START, END, IDX, MAX_ATTRS, MAX_LEN) \
+    for ((IDX) = 0, (OFF) = (void *)(ATTRS) - (START); \
+         (IDX) < (MAX_ATTRS) && (OFF) < (END) - (START); \
+         (IDX)++, (OFF) = bpf_map_nl_attr_next_offset(START, OFF, MAX_LEN))
+
+#endif /* bpf_netlink.h */
diff --git a/bpf/bpf_workaround.h b/bpf/bpf_workaround.h
new file mode 100644
index 000000000..cb072a7e6
--- /dev/null
+++ b/bpf/bpf_workaround.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2020 NTT Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BPF_WORKAROUND_H
+#define BPF_WORKAROUND_H
+
+/* On Linux x86/x64 systems bits/wordsize.h included from stdint.h cannot
+ * correctly determine __WORDSIZE for bpf, which causes incorrect UINTPTR_MAX
+ */
+#if __UINTPTR_MAX__ == __UINT64_MAX__ && defined(UINTPTR_MAX)
+#undef UINTPTR_MAX
+#define UINTPTR_MAX UINT64_MAX
+#endif
+
+#endif /* bpf_workaround.h */
diff --git a/bpf/flowtable_afxdp.c b/bpf/flowtable_afxdp.c
new file mode 100644
index 000000000..e87128ab1
--- /dev/null
+++ b/bpf/flowtable_afxdp.c
@@ -0,0 +1,585 @@
+/*
+ * Copyright (c) 2020 NTT Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* linux/types.h is necessary for bpf_helpers.h as it's not self-contained so
+ * that we can alternatively choose vmlinux.h auto-generated from BTF. */
+#include <linux/types.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/bpf.h>
+
+/* Workaround for incorrect macros for bpf in stdint.h */
+#include <stdint.h>
+#include "bpf_workaround.h"
+
+#include "bpf_compiler.h"
+#include "bpf_miniflow.h"
+#include "bpf_netlink.h"
+#include "netdev-offload-xdp.h"
+#include "packets.h"
+#include "util.h"
+
+/* Supported keys. Need to keep same 64-align as struct flow for miniflow */
+struct xdp_flow {
+    struct eth_addr dl_dst;
+    struct eth_addr dl_src;
+    ovs_be16 dl_type;
+    uint8_t pad1[2];
+
+    union flow_vlan_hdr vlans[1];
+    uint8_t pad2[4];
+
+    ovs_be32 nw_src;
+    ovs_be32 nw_dst;
+
+    uint8_t pad3[4];
+    uint8_t nw_frag;
+    uint8_t nw_tos;
+    uint8_t nw_ttl;
+    uint8_t nw_proto;
+
+    ovs_be16 tp_src;
+    ovs_be16 tp_dst;
+    uint8_t pad4[4];
+};
+
+/* Size of xdp_flow must be 64-aligned for key comparison */
+BUILD_ASSERT_DECL(sizeof(struct xdp_flow) % sizeof(uint64_t) == 0);
+
+#define XDP_FLOW_U64S (sizeof(struct xdp_flow) / sizeof(uint64_t))
+
+#define XDP_MAX_SUBTABLE_FLOWS 1024
+#define XDP_MAX_ACTIONS_LEN 256
+#define XDP_MAX_ACTIONS 32
+
+/* Actual key in each subtable. miniflow map is omitted as it's identical to
+ * mask map */
+struct xdp_flow_key {
+    /* Actually we can use smaller key than XDP_FLOW_U64S to minimize hash
+     * table search cost. It's possible because we rarely need all of
+     * combinations of flow keys. OVS XDP offload can properly handle
+     * smaller one. */
+    uint64_t miniflow_buf[XDP_FLOW_U64S];
+    /* Dummy. keep xdp_flow details in BTF */
+    struct xdp_flow _flow[];
+};
+
+/* Value for subtable mask array */
+struct xdp_subtable_mask {
+    struct xdp_subtable_mask_header header;
+    uint64_t buf[XDP_FLOW_U64S];
+};
+
+/* miniflow for packet */
+struct xdp_miniflow {
+    struct miniflow mf;
+    uint64_t miniflow_buf[XDP_FLOW_U64S];
+};
+
+/* Used when the action only modifies the packet */
+#define _XDP_ACTION_CONTINUE -1
+
+/* Supported actions */
+/* XXX: This size should be uint16_t but needs to be int as kernel has a bug
+ * in btf_enum_check_member() that assumes enum size is sizeof(int), which
+ * causes an error when loading BTF if we use uint16_t here */
+enum action_attrs : uint32_t {
+    XDP_ACTION_OUTPUT = OVS_ACTION_ATTR_OUTPUT,
+    XDP_ACTION_PUSH_VLAN = OVS_ACTION_ATTR_PUSH_VLAN,
+    XDP_ACTION_POP_VLAN = OVS_ACTION_ATTR_POP_VLAN,
+};
+
+struct xdp_flow_actions {
+    struct xdp_flow_actions_header header;
+    uint8_t data[XDP_MAX_ACTIONS_LEN - sizeof(struct xdp_flow_actions_header)];
+};
+
+/* A struct to inform vswitchd of metadata like supported keys/actions */
+struct xdp_meta_info {
+    __type(supported_keys, struct xdp_flow);
+    __type(supported_actions, enum action_attrs);
+    __uint(max_actions, XDP_MAX_ACTIONS);
+} meta_info SEC(".ovs_meta");
+
+
+/* Map definitions */
+
+struct {
+    __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+    __uint(max_entries, 256);
+    __type(key, uint32_t);
+    __type(value, long);
+} debug_stats SEC(".maps");
+
+/* Temporary storage for packet miniflow. Need this because verifier does not
+ * allow access to array variable in stack with variable index. Such access
+ * happens in mask_key() */
+struct {
+    __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+    __uint(max_entries, 1);
+    __type(key, uint32_t);
+    __type(value, struct xdp_miniflow);
+} pkt_mf_tbl SEC(".maps");
+
+struct {
+    __uint(type, BPF_MAP_TYPE_XSKMAP);
+    __uint(max_entries, 1); /* This should be redefined by userspace */
+    __uint(key_size, sizeof(int));
+    __uint(value_size, sizeof(int));
+} xsks_map SEC(".maps");
+
+struct {
+    __uint(type, BPF_MAP_TYPE_DEVMAP);
+    __uint(max_entries, XDP_MAX_PORTS);
+    __uint(key_size, sizeof(int));
+    __uint(value_size, sizeof(int));
+} output_map SEC(".maps");
+
+/* Head index for subtbl_masks list */
+/* TODO: Use global variable */
+struct {
+    __uint(type, BPF_MAP_TYPE_ARRAY);
+    __uint(max_entries, 1);
+    __type(key, uint32_t);
+    __type(value, int);
+} subtbl_masks_hd SEC(".maps");
+
+/* Information about subtable mask. A list implemented using array */
+struct {
+    __uint(type, BPF_MAP_TYPE_ARRAY);
+    __uint(max_entries, XDP_MAX_SUBTABLES);
+    __type(key, uint32_t);
+    __type(value, struct xdp_subtable_mask);
+} subtbl_masks SEC(".maps");
+
+/* Template for subtable hash-map. This will be used in userspace to create
+ * flow_table array-of-maps. */
+struct {
+    __uint(type, BPF_MAP_TYPE_HASH);
+    __uint(max_entries, XDP_MAX_SUBTABLE_FLOWS);
+    __type(key, struct xdp_flow_key);
+    __type(value, struct xdp_flow_actions);
+} subtbl_template SEC(".maps");
+
+/* Array-of-maps whose entry contains subtable hash-map. */
+struct {
+    __uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+    __uint(max_entries, XDP_MAX_SUBTABLES);
+    __uint(key_size, sizeof(uint32_t));
+    __uint(value_size, sizeof(uint32_t));
+} flow_table SEC(".maps");
+
+
+static inline void
+account_debug(int idx)
+{
+    long *cnt;
+
+    cnt = bpf_map_lookup_elem(&debug_stats, &idx);
+    if (cnt) {
+        *cnt += 1;
+    }
+}
+
+static inline void
+account_action(enum action_attrs act)
+{
+    account_debug(act + 1);
+}
+
+/* Derived from xsk_load_xdp_prog() in libbpf */
+static inline int
+upcall(struct xdp_md *ctx)
+{
+    int ret, index = ctx->rx_queue_index;
+
+    ret = bpf_redirect_map(&xsks_map, index, XDP_ABORTED);
+    if (ret > 0) {
+        return ret;
+    }
+
+    /* Fallback for kernel <= 5.3 not supporting default action in flags */
+    if (bpf_map_lookup_elem(&xsks_map, &index)) {
+        return bpf_redirect_map(&xsks_map, index, 0);
+    }
+
+    return XDP_ABORTED;
+}
+
+static inline int
+action_output(int tx_port)
+{
+    account_action(XDP_ACTION_OUTPUT);
+
+    return bpf_redirect_map(&output_map, tx_port, 0);
+}
+
+static inline int
+action_vlan_push(struct xdp_md *ctx,
+                 const struct ovs_action_push_vlan *vlan)
+{
+    struct vlan_eth_header *veh;
+    void *data, *data_end;
+    ovs_be16 tpid, tci;
+
+    account_action(XDP_ACTION_PUSH_VLAN);
+
+    tpid = vlan->vlan_tpid;
+    tci = vlan->vlan_tci;
+
+    if (bpf_xdp_adjust_head(ctx, -VLAN_HEADER_LEN)) {
+        return XDP_DROP;
+    }
+
+    data_end = (void *)(long)ctx->data_end;
+    data = (void *)(long)ctx->data;
+    if (data + VLAN_ETH_HEADER_LEN > data_end) {
+        return XDP_DROP;
+    }
+
+    __builtin_memmove(data, data + VLAN_HEADER_LEN, 2 * ETH_ADDR_LEN);
+    veh = data;
+    veh->veth_type = tpid;
+    veh->veth_tci = tci & htons(~VLAN_CFI);
+
+    return _XDP_ACTION_CONTINUE;
+}
+
+static inline int
+action_vlan_pop(struct xdp_md *ctx)
+{
+    struct vlan_eth_header *veh;
+    void *data, *data_end;
+
+    account_action(XDP_ACTION_POP_VLAN);
+
+    data_end = (void *)(long)ctx->data_end;
+    data = (void *)(long)ctx->data;
+    if (data + VLAN_ETH_HEADER_LEN > data_end) {
+        return _XDP_ACTION_CONTINUE;
+    }
+
+    veh = data;
+    if (!eth_type_vlan(veh->veth_type)) {
+        return _XDP_ACTION_CONTINUE;
+    }
+
+    __builtin_memmove(data + VLAN_HEADER_LEN, data, 2 * ETH_ADDR_LEN);
+    if (bpf_xdp_adjust_head(ctx, VLAN_HEADER_LEN)) {
+        return XDP_DROP;
+    }
+
+    return _XDP_ACTION_CONTINUE;
+}
+
+/* TODO: Add more actions */
+
+
+struct nw_params {
+    union {
+        ovs_be32 params;
+        struct {
+            uint8_t nw_frag;
+            uint8_t nw_tos;
+            uint8_t nw_ttl;
+            uint8_t nw_proto;
+        };
+    };
+};
+
+static inline int
+parse_ipv4(void *data, uint64_t *nh_off, void *data_end,
+           struct bpf_mf_ctx *mf_ctx, struct nw_params *nw_params)
+{
+    struct ip_header *ip = data + *nh_off;
+
+    if (ip + 1 > data_end) {
+        return 1;
+    }
+
+    /* Linux network drivers ensure that IP header is 4-byte aligned or
+     * the platform can handle unaligned access */
+    miniflow_push_be32(mf_ctx, nw_src, *(ovs_be32 *)(void *)&ip->ip_src);
+    miniflow_push_be32(mf_ctx, nw_dst, *(ovs_be32 *)(void *)&ip->ip_dst);
+
+    if (OVS_UNLIKELY(IP_IS_FRAGMENT(ip->ip_frag_off))) {
+        nw_params->nw_frag = FLOW_NW_FRAG_ANY;
+        if (ip->ip_frag_off & htons(IP_FRAG_OFF_MASK)) {
+            nw_params->nw_frag |= FLOW_NW_FRAG_LATER;
+        }
+    } else {
+        nw_params->nw_frag = 0;
+    }
+    nw_params->nw_tos = ip->ip_tos;
+    nw_params->nw_ttl = ip->ip_ttl;
+    nw_params->nw_proto = ip->ip_proto;
+
+    *nh_off += IP_IHL(ip->ip_ihl_ver) * 4;
+
+    return 0;
+}
+
+static inline int
+xdp_miniflow_extract(struct xdp_md *ctx, struct xdp_miniflow *pkt_mf)
+{
+    void *data = (void *)(long)ctx->data;
+    void *data_end = (void *)(long)ctx->data_end;
+    struct eth_header *eth = data;
+    struct vlan_header *vlan = NULL;
+    ovs_be16 dl_type;
+    uint64_t nh_off;
+    struct nw_params nw_params;
+    struct bpf_mf_ctx mf_ctx = { {{ 0 }}, (uint64_t *)&pkt_mf->miniflow_buf };
+
+    nh_off = sizeof *eth;
+    if (data + nh_off > data_end) {
+        return 1;
+    }
+
+    miniflow_push_macs(&mf_ctx, dl_dst, &eth->eth_dst);
+
+    if (eth_type_vlan(eth->eth_type)) {
+        vlan = data + nh_off;
+        nh_off += sizeof(*vlan);
+        if (data + nh_off > data_end) {
+            return 1;
+        }
+        dl_type = vlan->vlan_next_type;
+    } else {
+        dl_type = eth->eth_type;
+    }
+    miniflow_push_be16(&mf_ctx, dl_type, dl_type);
+    miniflow_pad_to_64(&mf_ctx, dl_type);
+
+    if (vlan) {
+        const ovs_16aligned_be32 *qp;
+        union flow_vlan_hdr vlan_hdr;
+
+        qp = (ovs_16aligned_be32 *)&eth->eth_type;
+        vlan_hdr.qtag = get_16aligned_be32(qp);
+        vlan_hdr.tci |= htons(VLAN_CFI);
+        miniflow_push_be32(&mf_ctx, vlans, vlan_hdr.qtag);
+        miniflow_push_be32_(&mf_ctx,
+                            offsetof(struct flow, vlans) + sizeof(ovs_be32),
+                            0);
+    }
+
+    if (dl_type == htons(ETH_TYPE_IP)) {
+        if (parse_ipv4(data, &nh_off, data_end, &mf_ctx, &nw_params)) {
+            return 1;
+        }
+    } else {
+        goto out;
+    }
+    miniflow_pad_from_64(&mf_ctx, nw_frag);
+    miniflow_push_be32(&mf_ctx, nw_frag, &nw_params.params);
+
+    if (nw_params.nw_proto == IPPROTO_TCP) {
+        struct tcp_header *tcp = data + nh_off;
+
+        if (tcp + 1 > data_end) {
+            return 1;
+        }
+
+        miniflow_push_be16(&mf_ctx, tp_src, tcp->tcp_src);
+        miniflow_push_be16(&mf_ctx, tp_dst, tcp->tcp_dst);
+    } else if (nw_params.nw_proto == IPPROTO_UDP) {
+        struct udp_header *udp = data + nh_off;
+
+        if (udp + 1 > data_end) {
+            return 1;
+        }
+
+        miniflow_push_be16(&mf_ctx, tp_src, udp->udp_src);
+        miniflow_push_be16(&mf_ctx, tp_dst, udp->udp_dst);
+    }
+out:
+    pkt_mf->mf.map = mf_ctx.map;
+    return 0;
+}
+
+#define for_each_subtable_mask(subtable_mask, head, idx, cnt) \
+    for (subtable_mask = bpf_map_lookup_elem(&subtbl_masks, (head)), \
+         idx = *(head), cnt = 0; \
+         subtable_mask != NULL && cnt < XDP_MAX_SUBTABLES; \
+         idx = subtable_mask->header.next, \
+         subtable_mask = bpf_map_lookup_elem(&subtbl_masks, &idx), cnt++)
+
+/* Returns false if an error happens */
+static inline int
+mask_key(uint64_t *mkey, const struct miniflow *pkt_mf,
+         const struct xdp_subtable_mask_header *tbl_mask)
+{
+    const struct miniflow *tbl_mf = &tbl_mask->mask.masks;
+    const uint64_t *tbl_blocks = miniflow_get_values(tbl_mf);
+    const uint64_t *pkt_blocks = miniflow_get_values(pkt_mf);
+    uint64_t tbl_mf_bits = tbl_mf->map.bits[0];
+    uint64_t pkt_mf_bits = pkt_mf->map.bits[0];
+    uint8_t tbl_mf_bits_u0 = tbl_mask->mf_bits_u0;
+    uint8_t tbl_mf_bits_u1 = tbl_mask->mf_bits_u1;
+    unsigned int pkt_ofs = 0;
+    int i = 0;
+
+    /* This sensitive loop easily exceeds verifier limit 1M insns so
+     * need to be careful when modifying.
+     * E.g. increasing XDP_FLOW_U64S by adding keys to struct xdp_flow
+     * increases verifier cost and may be rejected due to 1M insns exceeds */
+    for (; i < tbl_mf_bits_u0 + tbl_mf_bits_u1 && i < XDP_FLOW_U64S; i++) {
+        uint64_t mf_mask;
+        uint64_t idx_bits;
+        unsigned int pkt_idx;
+        uint64_t lowest_bit;
+
+        if (i == tbl_mf_bits_u0) {
+            tbl_mf_bits = tbl_mf->map.bits[1];
+            pkt_mf_bits = pkt_mf->map.bits[1];
+            pkt_ofs = count_1bits(pkt_mf->map.bits[0]);
+        }
+
+        lowest_bit = tbl_mf_bits & -tbl_mf_bits;
+        tbl_mf_bits &= ~lowest_bit;
+        if (!(lowest_bit & pkt_mf_bits)) {
+            mkey[i] = 0;
+            continue;
+        }
+        mf_mask = lowest_bit - 1;
+        idx_bits = mf_mask & pkt_mf_bits;
+        pkt_idx = count_1bits(idx_bits) + pkt_ofs;
+        if (pkt_idx >= XDP_FLOW_U64S) {
+            /* xdp flow api provider (userspace) BUG */
+            return false;
+        }
+
+        mkey[i] = pkt_blocks[pkt_idx] & tbl_blocks[i];
+    }
+
+    return true;
+}
+
+SEC("xdp") int
+flowtable_afxdp(struct xdp_md *ctx)
+{
+    struct xdp_miniflow *pkt_mf;
+    struct xdp_subtable_mask *subtable_mask;
+    int *head;
+    struct xdp_flow_actions *xdp_actions = NULL;
+    int cnt, i, idx, zero = 0;
+    struct nlattr *attrs;
+    size_t actions_len, offset;
+    void *start, *end;
+
+    account_debug(0);
+
+    head = bpf_map_lookup_elem(&subtbl_masks_hd, &zero);
+    if (!head) {
+        return XDP_ABORTED;
+    }
+    if (*head == XDP_SUBTABLES_TAIL) {
+        /* Offload not enabled */
+        goto upcall;
+    }
+
+    /* Get temporary storage for storing packet miniflow */
+    pkt_mf = bpf_map_lookup_elem(&pkt_mf_tbl, &zero);
+    if (!pkt_mf) {
+        return XDP_ABORTED;
+    }
+
+    /* Extract miniflow from packet */
+    if (xdp_miniflow_extract(ctx, pkt_mf)) {
+        return XDP_DROP;
+    }
+
+    /* Lookup each subtable */
+    for_each_subtable_mask(subtable_mask, head, idx, cnt) {
+        struct xdp_flow_key mkey = { 0 };
+        void *subtable;
+
+        subtable = bpf_map_lookup_elem(&flow_table, &idx);
+        if (!subtable) {
+            return XDP_ABORTED;
+        }
+
+        if (!mask_key(mkey.miniflow_buf, &pkt_mf->mf,
+                      &subtable_mask->header)) {
+            continue;
+        }
+
+        xdp_actions = bpf_map_lookup_elem(subtable, &mkey);
+        if (xdp_actions) {
+            break;
+        }
+    }
+
+    if (!xdp_actions) {
+        /* Flow entry miss */
+upcall:
+        return upcall(ctx);
+    }
+
+    /* Execute actions */
+    actions_len = xdp_actions->header.actions_len;
+    if (actions_len > XDP_MAX_ACTIONS_LEN -
+                      sizeof(struct xdp_flow_actions_header)) {
+        return XDP_ABORTED;
+    }
+    attrs = xdp_flow_actions(&xdp_actions->header);
+    start = xdp_actions;
+    end = (void *)attrs + actions_len;
+    BPF_MAP_NL_ATTR_FOR_EACH(offset, attrs, start, end, i, XDP_MAX_ACTIONS,
+                             XDP_MAX_ACTIONS_LEN) {
+        uint16_t type;
+        int act;
+        struct nlattr *nla;
+
+        if (offset > XDP_MAX_ACTIONS_LEN - sizeof(struct nlattr)) {
+            return XDP_ABORTED;
+        }
+        type = bpf_nl_attr_type((struct nlattr *)(start + offset));
+
+        switch ((enum action_attrs)type) {
+        case XDP_ACTION_OUTPUT:
+            bpf_compiler_reg_barrier(offset);
+            if (offset > XDP_MAX_ACTIONS_LEN - sizeof(struct nlattr) -
+                         sizeof(int)) {
+                return XDP_ABORTED;
+            }
+            nla = start + offset;
+            return action_output(*(int *)bpf_nl_attr_get(nla));
+        case XDP_ACTION_PUSH_VLAN:
+            bpf_compiler_reg_barrier(offset);
+            if (offset > XDP_MAX_ACTIONS_LEN - sizeof(struct nlattr) -
+                         sizeof(struct ovs_action_push_vlan)) {
+                return XDP_ABORTED;
+            }
+            nla = start + offset;
+            act = action_vlan_push(ctx, bpf_nl_attr_get(nla));
+            break;
+        case XDP_ACTION_POP_VLAN:
+            act = action_vlan_pop(ctx);
+            break;
+        default:
+            return XDP_ABORTED;
+        }
+        if (act != _XDP_ACTION_CONTINUE) {
+            return act;
+        }
+    }
+
+    account_debug(1);
+    return XDP_DROP;
+}
+
+char _license[] SEC("license") = "Apache-2.0";
diff --git a/configure.ac b/configure.ac
index 1877aae56..99a93ce00 100644
--- a/configure.ac
+++ b/configure.ac
@@ -99,6 +99,7 @@ OVS_CHECK_DOT
 OVS_CHECK_IF_DL
 OVS_CHECK_STRTOK_R
 OVS_CHECK_LINUX_AF_XDP
+OVS_CHECK_LINUX_BPF
 AC_CHECK_DECLS([sys_siglist], [], [], [[#include <signal.h>]])
 AC_CHECK_MEMBERS([struct stat.st_mtim.tv_nsec, struct stat.st_mtimensec],
   [], [], [[#include <sys/stat.h>]])
@@ -198,6 +199,7 @@ AC_CONFIG_FILES(datapath/Makefile)
 AC_CONFIG_FILES(datapath/linux/Kbuild)
 AC_CONFIG_FILES(datapath/linux/Makefile)
 AC_CONFIG_FILES(datapath/linux/Makefile.main)
+AC_CONFIG_FILES(bpf/Makefile)
 AC_CONFIG_FILES(tests/atlocal)
 AC_CONFIG_FILES(lib/libopenvswitch.pc)
 AC_CONFIG_FILES(lib/libsflow.pc)
-- 
2.25.1



More information about the dev mailing list