[netstack] Implement MSG_ERRQUEUE flag for recvmsg(2).

Introduces the per-socket error queue and the necessary cmsg mechanisms.

PiperOrigin-RevId: 348028508

1 files changed, 39 insertions, 0 deletions

diff --git a/pkg/sentry/socket/control/control.go b/pkg/sentry/socket/control/control.go
index b88cdca48..ff6b71802 100644
--- a/pkg/sentry/socket/control/control.go
+++ b/pkg/sentry/socket/control/control.go
@@ -371,6 +371,17 @@ func PackOriginalDstAddress(t *kernel.Task, originalDstAddress linux.SockAddr, b
 		buf, level, optType, t.Arch().Width(), originalDstAddress)
 }
 
+// PackSockExtendedErr packs an IP*_RECVERR socket control message.
+func PackSockExtendedErr(t *kernel.Task, sockErr linux.SockErrCMsg, buf []byte) []byte {
+	return putCmsgStruct(
+		buf,
+		sockErr.CMsgLevel(),
+		sockErr.CMsgType(),
+		t.Arch().Width(),
+		sockErr,
+	)
+}
+
 // PackControlMessages packs control messages into the given buffer.
 //
 // We skip control messages specific to Unix domain sockets.
@@ -403,6 +414,10 @@ func PackControlMessages(t *kernel.Task, cmsgs socket.ControlMessages, buf []byt
 		buf = PackOriginalDstAddress(t, cmsgs.IP.OriginalDstAddress, buf)
 	}
 
+	if cmsgs.IP.SockErr != nil {
+		buf = PackSockExtendedErr(t, cmsgs.IP.SockErr, buf)
+	}
+
 	return buf
 }
 
@@ -440,6 +455,10 @@ func CmsgsSpace(t *kernel.Task, cmsgs socket.ControlMessages) int {
 		space += cmsgSpace(t, cmsgs.IP.OriginalDstAddress.SizeBytes())
 	}
 
+	if cmsgs.IP.SockErr != nil {
+		space += cmsgSpace(t, cmsgs.IP.SockErr.SizeBytes())
+	}
+
 	return space
 }
 
@@ -546,6 +565,16 @@ func Parse(t *kernel.Task, socketOrEndpoint interface{}, buf []byte) (socket.Con
 				cmsgs.IP.OriginalDstAddress = &addr
 				i += binary.AlignUp(length, width)
 
+			case linux.IP_RECVERR:
+				var errCmsg linux.SockErrCMsgIPv4
+				if length < errCmsg.SizeBytes() {
+					return socket.ControlMessages{}, syserror.EINVAL
+				}
+
+				errCmsg.UnmarshalBytes(buf[i : i+errCmsg.SizeBytes()])
+				cmsgs.IP.SockErr = &errCmsg
+				i += binary.AlignUp(length, width)
+
 			default:
 				return socket.ControlMessages{}, syserror.EINVAL
 			}
@@ -568,6 +597,16 @@ func Parse(t *kernel.Task, socketOrEndpoint interface{}, buf []byte) (socket.Con
 				cmsgs.IP.OriginalDstAddress = &addr
 				i += binary.AlignUp(length, width)
 
+			case linux.IPV6_RECVERR:
+				var errCmsg linux.SockErrCMsgIPv6
+				if length < errCmsg.SizeBytes() {
+					return socket.ControlMessages{}, syserror.EINVAL
+				}
+
+				errCmsg.UnmarshalBytes(buf[i : i+errCmsg.SizeBytes()])
+				cmsgs.IP.SockErr = &errCmsg
+				i += binary.AlignUp(length, width)
+
 			default:
 				return socket.ControlMessages{}, syserror.EINVAL
 			}