bpf: Change bpf_setsockopt(SOL_IPV6) to reuse do_ipv6_setsockopt()

After the prep work in the previous patches,
this patch removes the dup code from bpf_setsockopt(SOL_IPV6)
and reuses the implementation in do_ipv6_setsockopt().

ipv6 could be compiled as a module.  Like how other code solved it
with stubs in ipv6_stubs.h, this patch adds the do_ipv6_setsockopt
to the ipv6_bpf_stub.

The current bpf_setsockopt(IPV6_TCLASS) does not take the
INET_ECN_MASK into the account for tcp.  The
do_ipv6_setsockopt(IPV6_TCLASS) will handle it correctly.

The existing optname white-list is refactored into a new
function sol_ipv6_setsockopt().

After this last SOL_IPV6 dup code removal, the __bpf_setsockopt()
is simplified enough that the extra "{ }" around the if statement
can be removed.
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220817061834.4181198-1-kafai@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

include/net/ipv6.h

@@ -1156,6 +1156,8 @@ struct in6_addr *fl6_update_dst(struct flowi6 *fl6,
  */
 DECLARE_STATIC_KEY_FALSE(ip6_min_hopcount);
 
+int do_ipv6_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
+		       unsigned int optlen);
 int ipv6_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
 		    unsigned int optlen);
 int ipv6_getsockopt(struct sock *sk, int level, int optname,

include/net/ipv6_stubs.h

@@ -81,6 +81,8 @@ struct ipv6_bpf_stub {
 				     const struct in6_addr *daddr, __be16 dport,
 				     int dif, int sdif, struct udp_table *tbl,
 				     struct sk_buff *skb);
+	int (*ipv6_setsockopt)(struct sock *sk, int level, int optname,
+			       sockptr_t optval, unsigned int optlen);
 };
 extern const struct ipv6_bpf_stub *ipv6_bpf_stub __read_mostly;
 

net/core/filter.c

@@ -5133,45 +5133,41 @@ static int sol_ip_setsockopt(struct sock *sk, int optname,
 				KERNEL_SOCKPTR(optval), optlen);
 }
 
+static int sol_ipv6_setsockopt(struct sock *sk, int optname,
+			       char *optval, int optlen)
+{
+	if (sk->sk_family != AF_INET6)
+		return -EINVAL;
+
+	switch (optname) {
+	case IPV6_TCLASS:
+		if (optlen != sizeof(int))
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ipv6_bpf_stub->ipv6_setsockopt(sk, SOL_IPV6, optname,
+					      KERNEL_SOCKPTR(optval), optlen);
+}
+
 static int __bpf_setsockopt(struct sock *sk, int level, int optname,
 			    char *optval, int optlen)
 {
-	int val, ret = 0;
-
 	if (!sk_fullsock(sk))
 		return -EINVAL;
 
-	if (level == SOL_SOCKET) {
+	if (level == SOL_SOCKET)
 		return sol_socket_setsockopt(sk, optname, optval, optlen);
-	} else if (IS_ENABLED(CONFIG_INET) && level == SOL_IP) {
+	else if (IS_ENABLED(CONFIG_INET) && level == SOL_IP)
 		return sol_ip_setsockopt(sk, optname, optval, optlen);
-	} else if (IS_ENABLED(CONFIG_IPV6) && level == SOL_IPV6) {
-		if (optlen != sizeof(int) || sk->sk_family != AF_INET6)
-			return -EINVAL;
-
-		val = *((int *)optval);
-		/* Only some options are supported */
-		switch (optname) {
-		case IPV6_TCLASS:
-			if (val < -1 || val > 0xff) {
-				ret = -EINVAL;
-			} else {
-				struct ipv6_pinfo *np = inet6_sk(sk);
-
-				if (val == -1)
-					val = 0;
-				np->tclass = val;
-			}
-			break;
-		default:
-			ret = -EINVAL;
-		}
-	} else if (IS_ENABLED(CONFIG_INET) && level == SOL_TCP) {
+	else if (IS_ENABLED(CONFIG_IPV6) && level == SOL_IPV6)
+		return sol_ipv6_setsockopt(sk, optname, optval, optlen);
+	else if (IS_ENABLED(CONFIG_INET) && level == SOL_TCP)
 		return sol_tcp_setsockopt(sk, optname, optval, optlen);
-	} else {
-		ret = -EINVAL;
-	}
-	return ret;
+
+	return -EINVAL;
 }
 
 static int _bpf_setsockopt(struct sock *sk, int level, int optname,

net/ipv6/af_inet6.c

@@ -1057,6 +1057,7 @@ static const struct ipv6_stub ipv6_stub_impl = {
 static const struct ipv6_bpf_stub ipv6_bpf_stub_impl = {
 	.inet6_bind = __inet6_bind,
 	.udp6_lib_lookup = __udp6_lib_lookup,
+	.ipv6_setsockopt = do_ipv6_setsockopt,
 };
 
 static int __init inet6_init(void)

net/ipv6/ipv6_sockglue.c

@@ -391,8 +391,8 @@ static int ipv6_set_opt_hdr(struct sock *sk, int optname, sockptr_t optval,
 	return err;
 }
 
-static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
-		   sockptr_t optval, unsigned int optlen)
+int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
+		       sockptr_t optval, unsigned int optlen)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct net *net = sock_net(sk);