net/af_xdp: revert use BPF link for XDP programs

The commit ae70cc6e893b ("net/af_xdp: use BPF link for XDP programs")
caused compilation errors on kernels older than v5.8 due to absence of
the bpf_link_info struct and some definitions in the linux/bpf.h header.
Since relying on the reported kernel version is not a robust solution
and also since there doesn't appear to be a suitable definition in the
bpf header that the preprocessor could rely on to determine support for
bpf link, we will take a different approach to solving the issue that
the original patch attempted to solve. The next commit will address
this.

Fixes: ae70cc6e893b ("net/af_xdp: use BPF link for XDP programs")
Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>

diff --git a/drivers/net/af_xdp/compat.h b/drivers/net/af_xdp/compat.h
index 1d66f5e318fa77ca63f9e211226dfcd5cebdaed0..3880dc7dd7f5b42b67ff6e0e6d31a4966f31a8bd 100644 (file)
--- a/drivers/net/af_xdp/compat.h
+++ b/drivers/net/af_xdp/compat.h
@@ -2,7 +2,6 @@
  * Copyright(c) 2020 Intel Corporation.
  */
 
-#include <bpf/bpf.h>
 #include <bpf/xsk.h>
 #include <linux/version.h>
 #include <poll.h>
@@ -55,126 +54,3 @@ tx_syscall_needed(struct xsk_ring_prod *q __rte_unused)
        return 1;
 }
 #endif
-
-#ifdef RTE_LIBRTE_AF_XDP_PMD_BPF_LINK
-static int link_lookup(int ifindex, int *link_fd)
-{
-       struct bpf_link_info link_info;
-       __u32 link_len;
-       __u32 id = 0;
-       int err;
-       int fd;
-
-       while (true) {
-               err = bpf_link_get_next_id(id, &id);
-               if (err) {
-                       if (errno == ENOENT) {
-                               err = 0;
-                               break;
-                       }
-                       break;
-               }
-
-               fd = bpf_link_get_fd_by_id(id);
-               if (fd < 0) {
-                       if (errno == ENOENT)
-                               continue;
-                       err = -errno;
-                       break;
-               }
-
-               link_len = sizeof(struct bpf_link_info);
-               memset(&link_info, 0, link_len);
-               err = bpf_obj_get_info_by_fd(fd, &link_info, &link_len);
-               if (err) {
-                       close(fd);
-                       break;
-               }
-               if (link_info.type == BPF_LINK_TYPE_XDP) {
-                       if ((int)link_info.xdp.ifindex == ifindex) {
-                               *link_fd = fd;
-                               break;
-                       }
-               }
-               close(fd);
-       }
-
-       return err;
-}
-
-static bool probe_bpf_link(void)
-{
-       DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts,
-                           .flags = XDP_FLAGS_SKB_MODE);
-       struct bpf_load_program_attr prog_attr;
-       struct bpf_insn insns[2];
-       int prog_fd, link_fd = -1;
-       int ifindex_lo = 1;
-       bool ret = false;
-       int err;
-
-       err = link_lookup(ifindex_lo, &link_fd);
-       if (err)
-               return ret;
-
-       if (link_fd >= 0)
-               return true;
-
-       /* BPF_MOV64_IMM(BPF_REG_0, XDP_PASS), */
-       insns[0].code = BPF_ALU64 | BPF_MOV | BPF_K;
-       insns[0].dst_reg = BPF_REG_0;
-       insns[0].imm = XDP_PASS;
-
-       /* BPF_EXIT_INSN() */
-       insns[1].code = BPF_JMP | BPF_EXIT;
-
-       memset(&prog_attr, 0, sizeof(prog_attr));
-       prog_attr.prog_type = BPF_PROG_TYPE_XDP;
-       prog_attr.insns = insns;
-       prog_attr.insns_cnt = RTE_DIM(insns);
-       prog_attr.license = "GPL";
-
-       prog_fd = bpf_load_program_xattr(&prog_attr, NULL, 0);
-       if (prog_fd < 0)
-               return ret;
-
-       link_fd = bpf_link_create(prog_fd, ifindex_lo, BPF_XDP, &opts);
-       close(prog_fd);
-
-       if (link_fd >= 0) {
-               ret = true;
-               close(link_fd);
-       }
-
-       return ret;
-}
-
-static int link_xdp_program(int if_index, int prog_fd, bool use_bpf_link)
-{
-       DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts);
-       int link_fd, ret = 0;
-
-       if (!use_bpf_link)
-               return bpf_set_link_xdp_fd(if_index, prog_fd,
-                                          XDP_FLAGS_UPDATE_IF_NOEXIST);
-
-       opts.flags = 0;
-       link_fd = bpf_link_create(prog_fd, if_index, BPF_XDP, &opts);
-       if (link_fd < 0)
-               ret = -1;
-
-       return ret;
-}
-#else
-static bool probe_bpf_link(void)
-{
-       return false;
-}
-
-static int link_xdp_program(int if_index, int prog_fd,
-                           bool use_bpf_link __rte_unused)
-{
-       return bpf_set_link_xdp_fd(if_index, prog_fd,
-                                  XDP_FLAGS_UPDATE_IF_NOEXIST);
-}
-#endif

diff --git a/drivers/net/af_xdp/meson.build b/drivers/net/af_xdp/meson.build
index 42dc6d69ac7ac5b6473492be71853971d506caa6..3ed2b29784aacba141a165a83457472e89ca12f0 100644 (file)
--- a/drivers/net/af_xdp/meson.build
+++ b/drivers/net/af_xdp/meson.build
@@ -16,18 +16,11 @@ endif
 
 if bpf_dep.found() and cc.has_header('bpf/xsk.h') and cc.has_header('linux/if_xdp.h')
     ext_deps += bpf_dep
-    # check for libbpf shared umem APIs
     bpf_ver_dep = dependency('libbpf', version : '>=0.2.0',
             required: false, method: 'pkg-config')
     if bpf_ver_dep.found()
         dpdk_conf.set('RTE_LIBRTE_AF_XDP_PMD_SHARED_UMEM', 1)
     endif
-    # check for libbpf bpf link support
-    bpf_link_dep = dependency('libbpf', version : '>=0.4.0',
-            required: false, method: 'pkg-config')
-    if bpf_link_dep.found()
-        dpdk_conf.set('RTE_LIBRTE_AF_XDP_PMD_BPF_LINK', 1)
-    endif
 else
     build = false
     reason = 'missing dependency, "libbpf"'

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 917e0bb453ba8e570c18062dc7d12c3bd8c0a373..1c7689c9b494e43d585e20c1dc4985e420f3cbf0 100644 (file)
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -139,7 +139,6 @@ struct pmd_internals {
        bool shared_umem;
        char prog_path[PATH_MAX];
        bool custom_prog_configured;
-       bool use_bpf_link;
 
        struct rte_ether_addr eth_addr;
 
@@ -973,8 +972,7 @@ eth_dev_close(struct rte_eth_dev *dev)
         */
        dev->data->mac_addrs = NULL;
 
-       if (!internals->use_bpf_link)
-               remove_xdp_program(internals);
+       remove_xdp_program(internals);
 
        if (internals->shared_umem) {
                struct internal_list *list;
@@ -1149,7 +1147,7 @@ err:
 }
 
 static int
-load_custom_xdp_prog(const char *prog_path, int if_index, bool use_bpf_link)
+load_custom_xdp_prog(const char *prog_path, int if_index)
 {
        int ret, prog_fd = -1;
        struct bpf_object *obj;
@@ -1173,7 +1171,8 @@ load_custom_xdp_prog(const char *prog_path, int if_index, bool use_bpf_link)
        }
 
        /* Link the program with the given network device */
-       ret = link_xdp_program(if_index, prog_fd, use_bpf_link);
+       ret = bpf_set_link_xdp_fd(if_index, prog_fd,
+                                       XDP_FLAGS_UPDATE_IF_NOEXIST);
        if (ret) {
                AF_XDP_LOG(ERR, "Failed to set prog fd %d on interface\n",
                                prog_fd);
@@ -1273,8 +1272,7 @@ xsk_configure(struct pmd_internals *internals, struct pkt_rx_queue *rxq,
        if (strnlen(internals->prog_path, PATH_MAX) &&
                                !internals->custom_prog_configured) {
                ret = load_custom_xdp_prog(internals->prog_path,
-                                          internals->if_index,
-                                          internals->use_bpf_link);
+                                          internals->if_index);
                if (ret) {
                        AF_XDP_LOG(ERR, "Failed to load custom XDP program %s\n",
                                        internals->prog_path);
@@ -1691,7 +1689,6 @@ init_internals(struct rte_vdev_device *dev, const char *if_name,
        strlcpy(internals->if_name, if_name, IFNAMSIZ);
        strlcpy(internals->prog_path, prog_path, PATH_MAX);
        internals->custom_prog_configured = 0;
-       internals->use_bpf_link = probe_bpf_link();
 
 #ifndef ETH_AF_XDP_SHARED_UMEM
        if (shared_umem) {