bpf: Enable BPF_PROG_TYPE_SK_REUSEPORT bpf prog in reuseport selection

This patch allows a BPF_PROG_TYPE_SK_REUSEPORT bpf prog to select a
SO_REUSEPORT sk from a BPF_MAP_TYPE_REUSEPORT_ARRAY introduced in
the earlier patch.  "bpf_run_sk_reuseport()" will return -ECONNREFUSED
when the BPF_PROG_TYPE_SK_REUSEPORT prog returns SK_DROP.
The callers, in inet[6]_hashtable.c and ipv[46]/udp.c, are modified to
handle this case and return NULL immediately instead of continuing the
sk search from its hashtable.

It re-uses the existing SO_ATTACH_REUSEPORT_EBPF setsockopt to attach
BPF_PROG_TYPE_SK_REUSEPORT.  The "sk_reuseport_attach_bpf()" will check
if the attaching bpf prog is in the new SK_REUSEPORT or the existing
SOCKET_FILTER type and then check different things accordingly.

One level of "__reuseport_attach_prog()" call is removed.  The
"sk_unhashed() && ..." and "sk->sk_reuseport_cb" tests are pushed
back to "reuseport_attach_prog()" in sock_reuseport.c.  sock_reuseport.c
seems to have more knowledge on those test requirements than filter.c.
In "reuseport_attach_prog()", after new_prog is attached to reuse->prog,
the old_prog (if any) is also directly freed instead of returning the
old_prog to the caller and asking the caller to free.

The sysctl_optmem_max check is moved back to the
"sk_reuseport_attach_filter()" and "sk_reuseport_attach_bpf()".
As of other bpf prog types, the new BPF_PROG_TYPE_SK_REUSEPORT is only
bounded by the usual "bpf_prog_charge_memlock()" during load time
instead of bounded by both bpf_prog_charge_memlock and sysctl_optmem_max.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

2 files changed, 13 insertions, 5 deletions

diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index 595ad408dba0..3d7c7460a0c5 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -191,7 +191,7 @@ struct sock *inet6_lookup_listener(struct net *net,
 				     saddr, sport, daddr, hnum,
 				     dif, sdif);
 	if (result)
-		return result;
+		goto done;
 
 	/* Lookup lhash2 with in6addr_any */
 
@@ -200,9 +200,10 @@ struct sock *inet6_lookup_listener(struct net *net,
 	if (ilb2->count > ilb->count)
 		goto port_lookup;
 
-	return inet6_lhash2_lookup(net, ilb2, skb, doff,
-				   saddr, sport, daddr, hnum,
-				   dif, sdif);
+	result = inet6_lhash2_lookup(net, ilb2, skb, doff,
+				     saddr, sport, daddr, hnum,
+				     dif, sdif);
+	goto done;
 
 port_lookup:
 	sk_for_each(sk, &ilb->head) {
@@ -214,12 +215,15 @@ port_lookup:
 				result = reuseport_select_sock(sk, phash,
 							       skb, doff);
 				if (result)
-					return result;
+					goto done;
 			}
 			result = sk;
 			hiscore = score;
 		}
 	}
+done:
+	if (unlikely(IS_ERR(result)))
+		return NULL;
 	return result;
 }
 EXPORT_SYMBOL_GPL(inet6_lookup_listener);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index f6b96956a8ed..83f4c77c79d8 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -235,6 +235,8 @@ struct sock *__udp6_lib_lookup(struct net *net,
 						  exact_dif, hslot2,
 						  skb);
 		}
+		if (unlikely(IS_ERR(result)))
+			return NULL;
 		return result;
 	}
 begin:
@@ -249,6 +251,8 @@ begin:
 						    saddr, sport);
 				result = reuseport_select_sock(sk, hash, skb,
 							sizeof(struct udphdr));
+				if (unlikely(IS_ERR(result)))
+					return NULL;
 				if (result)
 					return result;
 			}