linux: add tcp_cc_info and its related types

Author: costela

Diff for: unix/linux/types.go

@@ -112,6 +112,7 @@ struct termios2 {
 #include <linux/if_pppox.h>
 #include <linux/if_tun.h>
 #include <linux/if_xdp.h>
+#include <linux/inet_diag.h>
 #include <linux/ipc.h>
 #include <linux/kcm.h>
 #include <linux/keyctl.h>
@@ -724,6 +725,14 @@ type Ucred C.struct_ucred
 
 type TCPInfo C.struct_tcp_info
 
+type tcpCCInfo C.union_tcp_cc_info // union of the three types below
+
+type TCPVegasInfo C.struct_tcpvegas_info
+
+type TCPDCTCPInfo C.struct_tcp_dctcp_info
+
+type TCPBBRInfo C.struct_tcp_bbr_info
+
 type CanFilter C.struct_can_filter
 
 type ifreq C.struct_ifreq
@@ -765,6 +774,7 @@ const (
 	SizeofICMPv6Filter      = C.sizeof_struct_icmp6_filter
 	SizeofUcred             = C.sizeof_struct_ucred
 	SizeofTCPInfo           = C.sizeof_struct_tcp_info
+	SizeofTCPCCInfo         = C.sizeof_union_tcp_cc_info
 	SizeofCanFilter         = C.sizeof_struct_can_filter
 	SizeofTCPRepairOpt      = C.sizeof_struct_tcp_repair_opt
 )

Diff for: unix/syscall_linux.go

@@ -1295,6 +1295,20 @@ func GetsockoptTCPInfo(fd, level, opt int) (*TCPInfo, error) {
 	return &value, err
 }
 
+// GetsockoptTCPCCInfo returns algorithm specific congestion control information for the socket.
+// It requires a type parameter to specify the type of congestion control algorithm being used. E.g. for BBR:
+//
+//	info, err := unix.GetsockoptTCPCCInfo[TCPBBRInfo](fd, unix.IPPROTO_TCP, unix.TCP_CC_INFO)
+//
+// The socket's congestion control algorighm can be retrieved via [GetsockoptString] with the [TCP_CONGESTION] option.
+func GetsockoptTCPCCInfo[T TCPVegasInfo | TCPDCTCPInfo | TCPBBRInfo](fd, level, opt int) (*T, error) {
+	var value tcpCCInfo
+	vallen := _Socklen(SizeofTCPCCInfo)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
+	out := (*T)(unsafe.Pointer(&value[0]))
+	return out, err
+}
+
 // GetsockoptString returns the string value of the socket option opt for the
 // socket associated with fd at the given socket level.
 func GetsockoptString(fd, level, opt int) (string, error) {