Add a hook named update_socket_protocol in __sys_socket(), for bpf progs to attach to and update socket protocol. One user case is to force legacy TCP apps to create and use MPTCP sockets instead of TCP ones.
Signed-off-by: Geliang Tang geliang.tang@suse.com --- net/socket.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)
diff --git a/net/socket.c b/net/socket.c index 2b0e54b2405c..6837a517ac9f 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1644,11 +1644,37 @@ struct file *__sys_socket_file(int family, int type, int protocol) return sock_alloc_file(sock, flags, NULL); }
+/* + * A hook for bpf progs to attach to and update socket protocol. + * + * A static noinline declaration here could cause the compiler to optimize away + * the function. A global noinline declaration will keep the definition, but may + * optimize away the callsite. Therefore, __weak is needed to ensure that the + * call is still emitted, by telling the compiler that we don't know what the + * function might eventually be. + * + * __diag_* below are needed to dismiss the missing prototype warning. + */ +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "kfuncs which will be used in BPF programs"); + +__weak noinline int update_socket_protocol(int family, int type, int protocol) +{ + return protocol; +} + +__diag_pop(); + int __sys_socket(int family, int type, int protocol) { struct socket *sock; int flags;
+ protocol = update_socket_protocol(family, type, protocol); + if (protocol < 0 || protocol >= IPPROTO_MAX) + return -EINVAL; + sock = __sys_socket_create(family, type, protocol); if (IS_ERR(sock)) return PTR_ERR(sock);