Re: [PATCH bpf-next v4 1/2] bpf, xdp: make bpf_redirect_map() a map operation

From: Björn Töpel <redacted>

Currently the bpf_redirect_map() implementation dispatches to the
correct map-lookup function via a switch-statement. To avoid the
dispatching, this change adds bpf_redirect_map() as a map
operation. Each map provides its bpf_redirect_map() version, and
correct function is automatically selected by the BPF verifier.

A nice side-effect of the code movement is that the map lookup
functions are now local to the map implementation files, which removes
one additional function call.

Signed-off-by: Björn Töpel <redacted>
---
  include/linux/bpf.h    | 26 ++++++--------------------
  include/linux/filter.h | 27 +++++++++++++++++++++++++++
  include/net/xdp_sock.h | 19 -------------------
  kernel/bpf/cpumap.c    |  8 +++++++-
  kernel/bpf/devmap.c    | 16 ++++++++++++++--
  kernel/bpf/verifier.c  | 11 +++++++++--
  net/core/filter.c      | 39 +--------------------------------------
  net/xdp/xskmap.c       | 18 ++++++++++++++++++
  8 files changed, 82 insertions(+), 82 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index cccaef1088ea..a44ba904ca37 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h

@@ -117,6 +117,9 @@ struct bpf_map_ops {
  					   void *owner, u32 size);
  	struct bpf_local_storage __rcu ** (*map_owner_storage_ptr)(void *owner);
  
+	/* XDP helpers.*/
+	int (*xdp_redirect_map)(struct bpf_map *map, u32 ifindex, u64 flags);
+
  	/* map_meta_equal must be implemented for maps that can be
  	 * used as an inner map.  It is a runtime check to ensure
  	 * an inner map can be inserted to an outer map.

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1dda9d81f12c..96705a49225e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c

@@ -5409,7 +5409,8 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
  	    func_id != BPF_FUNC_map_delete_elem &&
  	    func_id != BPF_FUNC_map_push_elem &&
  	    func_id != BPF_FUNC_map_pop_elem &&
-	    func_id != BPF_FUNC_map_peek_elem)
+	    func_id != BPF_FUNC_map_peek_elem &&
+	    func_id != BPF_FUNC_redirect_map)
  		return 0;
  
  	if (map == NULL) {

@@ -11762,7 +11763,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
  		     insn->imm == BPF_FUNC_map_delete_elem ||
  		     insn->imm == BPF_FUNC_map_push_elem   ||
  		     insn->imm == BPF_FUNC_map_pop_elem    ||
-		     insn->imm == BPF_FUNC_map_peek_elem)) {
+		     insn->imm == BPF_FUNC_map_peek_elem   ||
+		     insn->imm == BPF_FUNC_redirect_map)) {
  			aux = &env->insn_aux_data[i + delta];
  			if (bpf_map_ptr_poisoned(aux))
  				goto patch_call_imm;

@@ -11804,6 +11806,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
  				     (int (*)(struct bpf_map *map, void *value))NULL));
  			BUILD_BUG_ON(!__same_type(ops->map_peek_elem,
  				     (int (*)(struct bpf_map *map, void *value))NULL));
+			BUILD_BUG_ON(!__same_type(ops->xdp_redirect_map,
+				     (int (*)(struct bpf_map *map, u32 ifindex, u64 flags))NULL));
  patch_map_ops_generic:
  			switch (insn->imm) {
  			case BPF_FUNC_map_lookup_elem:

@@ -11830,6 +11834,9 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
  				insn->imm = BPF_CAST_CALL(ops->map_peek_elem) -
  					    __bpf_call_base;
  				continue;
+			case BPF_FUNC_redirect_map:
+				insn->imm = BPF_CAST_CALL(ops->xdp_redirect_map) - __bpf_call_base;