Re: [PATCH bpf-next v2 5/9] bpf: sockmap: allow UDP sockets

Add basic psock hooks for UDP sockets. This allows adding and
removing sockets, as well as automatic removal on unhash and close.

sock_map_sk_state_allowed is called from the syscall path, and
ensures that only established or listening sockets are added.
No such check exists for the BPF path: we rely on sockets being
in particular states when a BPF sock ops hook is executed.
For the passive open hook this means that sockets are actually in
TCP_SYN_RECV state (and unhashed) when they are added to the
sock map.

UDP sockets are not saddled with this inconsistency, and so the
checks for both syscall and BPF path should be identical. Rather
than duplicating the logic into sock_map_sk_state_allowed merge
it with sock_map_sk_is_suitable.

Signed-off-by: Lorenz Bauer <redacted>
---
 MAINTAINERS         |  1 +
 include/linux/udp.h |  4 ++++
 net/core/sock_map.c | 52 ++++++++++++++++++++++++++------------------
 net/ipv4/Makefile   |  1 +
 net/ipv4/udp_bpf.c  | 53 +++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 90 insertions(+), 21 deletions(-)
 create mode 100644 net/ipv4/udp_bpf.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 2af5fa73155e..495ba52038ad 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -9358,6 +9358,7 @@ F:	include/linux/skmsg.h
 F:	net/core/skmsg.c
 F:	net/core/sock_map.c
 F:	net/ipv4/tcp_bpf.c
+F:	net/ipv4/udp_bpf.c
 
 LANTIQ / INTEL Ethernet drivers
 M:	Hauke Mehrtens <hauke@hauke-m.de>

diff --git a/include/linux/udp.h b/include/linux/udp.h
index aa84597bdc33..2485a35d113c 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h

@@ -143,4 +143,8 @@ static inline bool udp_unexpected_gso(struct sock *sk, struct sk_buff *skb)
 
 #define IS_UDPLITE(__sk) (__sk->sk_protocol == IPPROTO_UDPLITE)
 
+#ifdef CONFIG_BPF_STREAM_PARSER
+int udp_bpf_init(struct sock *sk);
+#endif
+
 #endif	/* _LINUX_UDP_H */

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index c84cc9fc7f6b..d742e1538ae9 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c

@@ -466,15 +479,20 @@ static bool sock_map_op_okay(const struct bpf_sock_ops_kern *ops)
 	       ops->op == BPF_SOCK_OPS_TCP_LISTEN_CB;
 }
 
-static bool sock_map_sk_is_suitable(const struct sock *sk)
+static bool sock_map_sk_is_udp(const struct sock *sk)
 {
-	return sk->sk_type == SOCK_STREAM &&
-	       sk->sk_protocol == IPPROTO_TCP;
+	return sk->sk_type == SOCK_DGRAM && sk->sk_protocol == IPPROTO_UDP;
 }
 
-static bool sock_map_sk_state_allowed(const struct sock *sk)
+static bool sock_map_sk_is_suitable(const struct sock *sk, bool from_bpf)