flow_dissector: Make 'bpf_flow_dissect' return the bpf program retcode

Let 'bpf_flow_dissect' callers know the BPF program's retcode and act
accordingly.
Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20220821113519.116765-2-shmulik.ladkani@gmail.com

include/linux/skbuff.h

@@ -1460,8 +1460,8 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
 			     unsigned int key_count);
 
 struct bpf_flow_dissector;
-bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
-		      __be16 proto, int nhoff, int hlen, unsigned int flags);
+u32 bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
+		     __be16 proto, int nhoff, int hlen, unsigned int flags);
 
 bool __skb_flow_dissect(const struct net *net,
 			const struct sk_buff *skb,

net/bpf/test_run.c

@@ -1445,7 +1445,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 	bpf_test_timer_enter(&t);
 	do {
 		retval = bpf_flow_dissect(prog, &ctx, eth->h_proto, ETH_HLEN,
-					  size, flags);
+					  size, flags) == BPF_OK;
 	} while (bpf_test_timer_continue(&t, 1, repeat, &ret, &duration));
 	bpf_test_timer_leave(&t);
 

net/core/flow_dissector.c

@@ -866,8 +866,8 @@ static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
 	}
 }
 
-bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
-		      __be16 proto, int nhoff, int hlen, unsigned int flags)
+u32 bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
+		     __be16 proto, int nhoff, int hlen, unsigned int flags)
 {
 	struct bpf_flow_keys *flow_keys = ctx->flow_keys;
 	u32 result;
@@ -892,7 +892,7 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
 	flow_keys->thoff = clamp_t(u16, flow_keys->thoff,
 				   flow_keys->nhoff, hlen);
 
-	return result == BPF_OK;
+	return result;
 }
 
 static bool is_pppoe_ses_hdr_valid(const struct pppoe_hdr *hdr)
@@ -1008,6 +1008,7 @@ bool __skb_flow_dissect(const struct net *net,
 			};
 			__be16 n_proto = proto;
 			struct bpf_prog *prog;
+			u32 result;
 
 			if (skb) {
 				ctx.skb = skb;
@@ -1019,12 +1020,12 @@ bool __skb_flow_dissect(const struct net *net,
 			}
 
 			prog = READ_ONCE(run_array->items[0].prog);
-			ret = bpf_flow_dissect(prog, &ctx, n_proto, nhoff,
-					       hlen, flags);
+			result = bpf_flow_dissect(prog, &ctx, n_proto, nhoff,
+						  hlen, flags);
 			__skb_flow_bpf_to_target(&flow_keys, flow_dissector,
 						 target_container);
 			rcu_read_unlock();
-			return ret;
+			return result == BPF_OK;
 		}
 		rcu_read_unlock();
 	}