[PATCH bpf-next 1/3] bpf/bpf_get,set_sockopt: add option to set TCP-BPF sock ops flags

Alan Maguire
2024-08-02T15:29:59Z

Currently the only opportunity to set sock ops flags dictating
which callbacks fire for a socket is from within a TCP-BPF sockops
program. This is problematic if the connection is already set up
as there is no further chance to specify callbacks for that socket.
Add TCP_BPF_SOCK_OPS_CB_FLAGS to bpf_setsockopt() and bpf_getsockopt()
to allow users to specify callbacks later, either via an iterator
over sockets or via a socket-specific program triggered by a
setsockopt() on the socket.

Previous discussion on this here [1].

[1] https://lore.kernel.org/bpf/f42f157b-6e52-dd4d-3d97-9b86c84c0b00@oracle.com/

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
include/uapi/linux/bpf.h | 3 ++-
net/core/filter.c | 16 ++++++++++++++++
tools/include/uapi/linux/bpf.h | 3 ++-
3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 35bcf52dbc65..d4d7efc34e67 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2851,7 +2851,7 @@ union bpf_attr {
* **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**,
* **TCP_NODELAY**, **TCP_MAXSEG**, **TCP_WINDOW_CLAMP**,
* **TCP_THIN_LINEAR_TIMEOUTS**, **TCP_BPF_DELACK_MAX**,
- * **TCP_BPF_RTO_MIN**.
+ * **TCP_BPF_RTO_MIN**, **TCP_BPF_SOCK_OPS_CB_FLAGS**.
* * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
* * **IPPROTO_IPV6**, which supports the following *optname*\ s:
* **IPV6_TCLASS**, **IPV6_AUTOFLOWLABEL**.
@@ -7080,6 +7080,7 @@ enum {
TCP_BPF_SYN = 1005, /* Copy the TCP header */
TCP_BPF_SYN_IP = 1006, /* Copy the IP[46] and TCP header */
TCP_BPF_SYN_MAC = 1007, /* Copy the MAC, IP[46], and TCP header */
+ TCP_BPF_SOCK_OPS_CB_FLAGS = 1008, /* Set TCP sock ops flags */
};

enum {
diff --git a/net/core/filter.c b/net/core/filter.c
index 78a6f746ea0b..570ca3f12175 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5278,6 +5278,11 @@ static int bpf_sol_tcp_setsockopt(struct sock *sk, int optname,
return -EINVAL;
inet_csk(sk)->icsk_rto_min = timeout;
break;
+ case TCP_BPF_SOCK_OPS_CB_FLAGS:
+ if (val & ~(BPF_SOCK_OPS_ALL_CB_FLAGS))
+ return -EINVAL;
+ tp->bpf_sock_ops_cb_flags = val;
+ break;
default:
return -EINVAL;
}
@@ -5366,6 +5371,17 @@ static int sol_tcp_sockopt(struct sock *sk, int optname,
if (*optlen < 1)
return -EINVAL;
break;
+ case TCP_BPF_SOCK_OPS_CB_FLAGS:
+ if (*optlen != sizeof(int))
+ return -EINVAL;
+ if (getopt) {
+ struct tcp_sock *tp = tcp_sk(sk);
+ int val = READ_ONCE(tp->bpf_sock_ops_cb_flags);
+
+ memcpy(optval, &val, *optlen);
+ return 0;
+ }
+ return bpf_sol_tcp_setsockopt(sk, optname, optval, *optlen);
default:
if (getopt)
return -EINVAL;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 35bcf52dbc65..d4d7efc34e67 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2851,7 +2851,7 @@ union bpf_attr {
* **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**,
* **TCP_NODELAY**, **TCP_MAXSEG**, **TCP_WINDOW_CLAMP**,
* **TCP_THIN_LINEAR_TIMEOUTS**, **TCP_BPF_DELACK_MAX**,
- * **TCP_BPF_RTO_MIN**.
+ * **TCP_BPF_RTO_MIN**, **TCP_BPF_SOCK_OPS_CB_FLAGS**.
* * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
* * **IPPROTO_IPV6**, which supports the following *optname*\ s:
* **IPV6_TCLASS**, **IPV6_AUTOFLOWLABEL**.
@@ -7080,6 +7080,7 @@ enum {
TCP_BPF_SYN = 1005, /* Copy the TCP header */
TCP_BPF_SYN_IP = 1006, /* Copy the IP[46] and TCP header */
TCP_BPF_SYN_MAC = 1007, /* Copy the MAC, IP[46], and TCP header */
+ TCP_BPF_SOCK_OPS_CB_FLAGS = 1008, /* Set TCP sock ops flags */
};

enum {
--
2.31.1