[netstack] Make tcpip.Error savable.

Earlier we could not save tcpip.Error objects in structs because upon restore
the constant's address changes in netstack's error translation map and
translating the error would panic because the map is based on the address of the
tcpip.Error instead of the error itself.

Now I made that translations map use the error message as key instead of the
address. Added relevant synchronization mechanisms to protect the structure
and initialize it upon restore.

PiperOrigin-RevId: 346590485

2 files changed, 56 insertions, 42 deletions

diff --git a/pkg/syserr/netstack.go b/pkg/syserr/netstack.go
index 5ae10939d..77c3c110c 100644
--- a/pkg/syserr/netstack.go
+++ b/pkg/syserr/netstack.go
@@ -15,6 +15,8 @@
 package syserr
 
 import (
+	"fmt"
+
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
@@ -48,45 +50,56 @@ var (
 	ErrNotPermittedNet       = New(tcpip.ErrNotPermitted.String(), linux.EPERM)
 )
 
-var netstackErrorTranslations = map[*tcpip.Error]*Error{
-	tcpip.ErrUnknownProtocol:           ErrUnknownProtocol,
-	tcpip.ErrUnknownNICID:              ErrUnknownNICID,
-	tcpip.ErrUnknownDevice:             ErrUnknownDevice,
-	tcpip.ErrUnknownProtocolOption:     ErrUnknownProtocolOption,
-	tcpip.ErrDuplicateNICID:            ErrDuplicateNICID,
-	tcpip.ErrDuplicateAddress:          ErrDuplicateAddress,
-	tcpip.ErrNoRoute:                   ErrNoRoute,
-	tcpip.ErrBadLinkEndpoint:           ErrBadLinkEndpoint,
-	tcpip.ErrAlreadyBound:              ErrAlreadyBound,
-	tcpip.ErrInvalidEndpointState:      ErrInvalidEndpointState,
-	tcpip.ErrAlreadyConnecting:         ErrAlreadyConnecting,
-	tcpip.ErrAlreadyConnected:          ErrAlreadyConnected,
-	tcpip.ErrNoPortAvailable:           ErrNoPortAvailable,
-	tcpip.ErrPortInUse:                 ErrPortInUse,
-	tcpip.ErrBadLocalAddress:           ErrBadLocalAddress,
-	tcpip.ErrClosedForSend:             ErrClosedForSend,
-	tcpip.ErrClosedForReceive:          ErrClosedForReceive,
-	tcpip.ErrWouldBlock:                ErrWouldBlock,
-	tcpip.ErrConnectionRefused:         ErrConnectionRefused,
-	tcpip.ErrTimeout:                   ErrTimeout,
-	tcpip.ErrAborted:                   ErrAborted,
-	tcpip.ErrConnectStarted:            ErrConnectStarted,
-	tcpip.ErrDestinationRequired:       ErrDestinationRequired,
-	tcpip.ErrNotSupported:              ErrNotSupported,
-	tcpip.ErrQueueSizeNotSupported:     ErrQueueSizeNotSupported,
-	tcpip.ErrNotConnected:              ErrNotConnected,
-	tcpip.ErrConnectionReset:           ErrConnectionReset,
-	tcpip.ErrConnectionAborted:         ErrConnectionAborted,
-	tcpip.ErrNoSuchFile:                ErrNoSuchFile,
-	tcpip.ErrInvalidOptionValue:        ErrInvalidOptionValue,
-	tcpip.ErrNoLinkAddress:             ErrHostDown,
-	tcpip.ErrBadAddress:                ErrBadAddress,
-	tcpip.ErrNetworkUnreachable:        ErrNetworkUnreachable,
-	tcpip.ErrMessageTooLong:            ErrMessageTooLong,
-	tcpip.ErrNoBufferSpace:             ErrNoBufferSpace,
-	tcpip.ErrBroadcastDisabled:         ErrBroadcastDisabled,
-	tcpip.ErrNotPermitted:              ErrNotPermittedNet,
-	tcpip.ErrAddressFamilyNotSupported: ErrAddressFamilyNotSupported,
+var netstackErrorTranslations map[string]*Error
+
+func addErrMapping(tcpipErr *tcpip.Error, netstackErr *Error) {
+	key := tcpipErr.String()
+	if _, ok := netstackErrorTranslations[key]; ok {
+		panic(fmt.Sprintf("duplicate error key: %s", key))
+	}
+	netstackErrorTranslations[key] = netstackErr
+}
+
+func init() {
+	netstackErrorTranslations = make(map[string]*Error)
+	addErrMapping(tcpip.ErrUnknownProtocol, ErrUnknownProtocol)
+	addErrMapping(tcpip.ErrUnknownNICID, ErrUnknownNICID)
+	addErrMapping(tcpip.ErrUnknownDevice, ErrUnknownDevice)
+	addErrMapping(tcpip.ErrUnknownProtocolOption, ErrUnknownProtocolOption)
+	addErrMapping(tcpip.ErrDuplicateNICID, ErrDuplicateNICID)
+	addErrMapping(tcpip.ErrDuplicateAddress, ErrDuplicateAddress)
+	addErrMapping(tcpip.ErrNoRoute, ErrNoRoute)
+	addErrMapping(tcpip.ErrBadLinkEndpoint, ErrBadLinkEndpoint)
+	addErrMapping(tcpip.ErrAlreadyBound, ErrAlreadyBound)
+	addErrMapping(tcpip.ErrInvalidEndpointState, ErrInvalidEndpointState)
+	addErrMapping(tcpip.ErrAlreadyConnecting, ErrAlreadyConnecting)
+	addErrMapping(tcpip.ErrAlreadyConnected, ErrAlreadyConnected)
+	addErrMapping(tcpip.ErrNoPortAvailable, ErrNoPortAvailable)
+	addErrMapping(tcpip.ErrPortInUse, ErrPortInUse)
+	addErrMapping(tcpip.ErrBadLocalAddress, ErrBadLocalAddress)
+	addErrMapping(tcpip.ErrClosedForSend, ErrClosedForSend)
+	addErrMapping(tcpip.ErrClosedForReceive, ErrClosedForReceive)
+	addErrMapping(tcpip.ErrWouldBlock, ErrWouldBlock)
+	addErrMapping(tcpip.ErrConnectionRefused, ErrConnectionRefused)
+	addErrMapping(tcpip.ErrTimeout, ErrTimeout)
+	addErrMapping(tcpip.ErrAborted, ErrAborted)
+	addErrMapping(tcpip.ErrConnectStarted, ErrConnectStarted)
+	addErrMapping(tcpip.ErrDestinationRequired, ErrDestinationRequired)
+	addErrMapping(tcpip.ErrNotSupported, ErrNotSupported)
+	addErrMapping(tcpip.ErrQueueSizeNotSupported, ErrQueueSizeNotSupported)
+	addErrMapping(tcpip.ErrNotConnected, ErrNotConnected)
+	addErrMapping(tcpip.ErrConnectionReset, ErrConnectionReset)
+	addErrMapping(tcpip.ErrConnectionAborted, ErrConnectionAborted)
+	addErrMapping(tcpip.ErrNoSuchFile, ErrNoSuchFile)
+	addErrMapping(tcpip.ErrInvalidOptionValue, ErrInvalidOptionValue)
+	addErrMapping(tcpip.ErrNoLinkAddress, ErrHostDown)
+	addErrMapping(tcpip.ErrBadAddress, ErrBadAddress)
+	addErrMapping(tcpip.ErrNetworkUnreachable, ErrNetworkUnreachable)
+	addErrMapping(tcpip.ErrMessageTooLong, ErrMessageTooLong)
+	addErrMapping(tcpip.ErrNoBufferSpace, ErrNoBufferSpace)
+	addErrMapping(tcpip.ErrBroadcastDisabled, ErrBroadcastDisabled)
+	addErrMapping(tcpip.ErrNotPermitted, ErrNotPermittedNet)
+	addErrMapping(tcpip.ErrAddressFamilyNotSupported, ErrAddressFamilyNotSupported)
 }
 
 // TranslateNetstackError converts an error from the tcpip package to a sentry
@@ -95,7 +108,7 @@ func TranslateNetstackError(err *tcpip.Error) *Error {
 	if err == nil {
 		return nil
 	}
-	se, ok := netstackErrorTranslations[err]
+	se, ok := netstackErrorTranslations[err.String()]
 	if !ok {
 		panic("Unknown error: " + err.String())
 	}
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 2bd472811..23e597365 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -49,8 +49,9 @@ const ipv4AddressSize = 4
 // Error represents an error in the netstack error space. Using a special type
 // ensures that errors outside of this space are not accidentally introduced.
 //
-// Note: to support save / restore, it is important that all tcpip errors have
-// distinct error messages.
+// All errors must have unique msg strings.
+//
+// +stateify savable
 type Error struct {
 	msg string