[PATCH bpf-next v4 1/2] bpf: Fix bpf_get/setsockopt to tos for ipv4-mapped ipv6 socket

[Leon Hwang <leon.hwang@linux.dev>]

When TCP over IPv4 via INET6 API, bpf_get/setsockopt with ipv4 will
fail, because sk->sk_family is AF_INET6. With ipv6 will success, not
take effect, because inet_csk(sk)->icsk_af_ops is ipv6_mapped and
use ip_queue_xmit, inet_sk(sk)->tos.

To relax this restriction, allow getting/setting tos for those possible
ipv4-mapped ipv6 sockets.

Fixes: ee7f1e1302f5 ("bpf: Change bpf_setsockopt(SOL_IP) to reuse do_ip_setsockopt()")
Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 net/core/filter.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 9590877b0714..57b00c6cc8cc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5544,11 +5544,24 @@ static int sol_tcp_sockopt(struct sock *sk, int optname,
 				 KERNEL_SOCKPTR(optval), *optlen);
 }
 
+static bool sk_allows_sol_ip_sockopt(struct sock *sk)
+{
+	switch (sk->sk_family) {
+	case AF_INET:
+		return true;
+	case AF_INET6:
+		/* Allow getting/setting sockopt for possible ipv4-mapped ipv6 socket. */
+		return sk->sk_type != SOCK_RAW && !ipv6_only_sock(sk);
+	default:
+		return false;
+	}
+}
+
 static int sol_ip_sockopt(struct sock *sk, int optname,
 			  char *optval, int *optlen,
 			  bool getopt)
 {
-	if (sk->sk_family != AF_INET)
+	if (!sk_allows_sol_ip_sockopt(sk))
 		return -EINVAL;
 
 	switch (optname) {
-- 
2.54.0