linux: add tcp_cc_info and its related types

Add the ability to retrieve congestion control information from a socket via TCP_CC_INFO.

Fixes golang/go#68232

Change-Id: I2ea15928ec0e3192b670759bab4b659e62be553b
GitHub-Last-Rev: b8b8c44
GitHub-Pull-Request: #200
Reviewed-on: https://go-review.googlesource.com/c/sys/+/595676
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

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>
@@ -757,6 +758,12 @@ type Ucred C.struct_ucred
 
 type TCPInfo C.struct_tcp_info
 
+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
@@ -798,6 +805,7 @@ 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
 )

unix/syscall_linux.go

@@ -1295,6 +1295,48 @@ func GetsockoptTCPInfo(fd, level, opt int) (*TCPInfo, error) {
 	return &value, err
 }
 
+// GetsockoptTCPCCVegasInfo returns algorithm specific congestion control information for a socket using the "vegas"
+// algorithm.
+//
+// The socket's congestion control algorighm can be retrieved via [GetsockoptString] with the [TCP_CONGESTION] option:
+//
+//	algo, err := unix.GetsockoptString(fd, unix.IPPROTO_TCP, unix.TCP_CONGESTION)
+func GetsockoptTCPCCVegasInfo(fd, level, opt int) (*TCPVegasInfo, error) {
+	var value [SizeofTCPCCInfo / 4]uint32 // ensure proper alignment
+	vallen := _Socklen(SizeofTCPCCInfo)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
+	out := (*TCPVegasInfo)(unsafe.Pointer(&value[0]))
+	return out, err
+}
+
+// GetsockoptTCPCCDCTCPInfo returns algorithm specific congestion control information for a socket using the "dctp"
+// algorithm.
+//
+// The socket's congestion control algorighm can be retrieved via [GetsockoptString] with the [TCP_CONGESTION] option:
+//
+//	algo, err := unix.GetsockoptString(fd, unix.IPPROTO_TCP, unix.TCP_CONGESTION)
+func GetsockoptTCPCCDCTCPInfo(fd, level, opt int) (*TCPDCTCPInfo, error) {
+	var value [SizeofTCPCCInfo / 4]uint32 // ensure proper alignment
+	vallen := _Socklen(SizeofTCPCCInfo)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
+	out := (*TCPDCTCPInfo)(unsafe.Pointer(&value[0]))
+	return out, err
+}
+
+// GetsockoptTCPCCBBRInfo returns algorithm specific congestion control information for a socket using the "bbr"
+// algorithm.
+//
+// The socket's congestion control algorighm can be retrieved via [GetsockoptString] with the [TCP_CONGESTION] option:
+//
+//	algo, err := unix.GetsockoptString(fd, unix.IPPROTO_TCP, unix.TCP_CONGESTION)
+func GetsockoptTCPCCBBRInfo(fd, level, opt int) (*TCPBBRInfo, error) {
+	var value [SizeofTCPCCInfo / 4]uint32 // ensure proper alignment
+	vallen := _Socklen(SizeofTCPCCInfo)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
+	out := (*TCPBBRInfo)(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) {