[go-marshal] Add dynamic tag in go_marshal.

This makes it easier to implement dynamically sized types in go-marshal. You
really only need to implement MarshalBytes, UnmarshalBytes and SizeBytes to
implement the entire interface.

By using the `dynamic` tag, the autogenerator will generate the rest of the
methods for us.

This change also simplifies how KernelIPTGetEntries implements Marshallable
using the newly added utility.

PiperOrigin-RevId: 356397114

3 files changed, 10 insertions, 131 deletions

diff --git a/pkg/abi/linux/BUILD b/pkg/abi/linux/BUILD
index 8fa61d6f7..ecaeb11ac 100644
--- a/pkg/abi/linux/BUILD
+++ b/pkg/abi/linux/BUILD
@@ -80,7 +80,6 @@ go_library(
         "//pkg/bits",
         "//pkg/marshal",
         "//pkg/marshal/primitive",
-        "//pkg/usermem",
     ],
 )
 
diff --git a/pkg/abi/linux/netfilter.go b/pkg/abi/linux/netfilter.go
index b521144d9..378f1baf3 100644
--- a/pkg/abi/linux/netfilter.go
+++ b/pkg/abi/linux/netfilter.go
@@ -15,11 +15,8 @@
 package linux
 
 import (
-	"io"
-
 	"gvisor.dev/gvisor/pkg/marshal"
 	"gvisor.dev/gvisor/pkg/marshal/primitive"
-	"gvisor.dev/gvisor/pkg/usermem"
 )
 
 // This file contains structures required to support netfilter, specifically
@@ -129,8 +126,8 @@ type IPTEntry struct {
 const SizeOfIPTEntry = 112
 
 // KernelIPTEntry is identical to IPTEntry, but includes the Elems field.
-// KernelIPTEntry itself is not Marshallable but it implements some methods of
-// marshal.Marshallable that help in other implementations of Marshallable.
+//
+// +marshal dynamic
 type KernelIPTEntry struct {
 	Entry IPTEntry
 
@@ -158,6 +155,8 @@ func (ke *KernelIPTEntry) UnmarshalBytes(src []byte) {
 	ke.Elems.UnmarshalBytes(src[ke.Entry.SizeBytes():])
 }
 
+var _ marshal.Marshallable = (*KernelIPTEntry)(nil)
+
 // IPTIP contains information for matching a packet's IP header.
 // It corresponds to struct ipt_ip in
 // include/uapi/linux/netfilter_ipv4/ip_tables.h.
@@ -411,8 +410,9 @@ type IPTGetEntries struct {
 const SizeOfIPTGetEntries = 40
 
 // KernelIPTGetEntries is identical to IPTGetEntries, but includes the
-// Entrytable field. This has been manually made marshal.Marshallable since it
-// is dynamically sized.
+// Entrytable field.
+//
+// +marshal dynamic
 type KernelIPTGetEntries struct {
 	IPTGetEntries
 	Entrytable []KernelIPTEntry
@@ -447,65 +447,6 @@ func (ke *KernelIPTGetEntries) UnmarshalBytes(src []byte) {
 	}
 }
 
-// Packed implements marshal.Marshallable.Packed.
-func (ke *KernelIPTGetEntries) Packed() bool {
-	// KernelIPTGetEntries isn't packed because the ke.Entrytable contains an
-	// indirection to the actual data we want to marshal (the slice data
-	// pointer), and the memory for KernelIPTGetEntries contains the slice
-	// header which we don't want to marshal.
-	return false
-}
-
-// MarshalUnsafe implements marshal.Marshallable.MarshalUnsafe.
-func (ke *KernelIPTGetEntries) MarshalUnsafe(dst []byte) {
-	// Fall back to safe Marshal because the type in not packed.
-	ke.MarshalBytes(dst)
-}
-
-// UnmarshalUnsafe implements marshal.Marshallable.UnmarshalUnsafe.
-func (ke *KernelIPTGetEntries) UnmarshalUnsafe(src []byte) {
-	// Fall back to safe Unmarshal because the type in not packed.
-	ke.UnmarshalBytes(src)
-}
-
-// CopyIn implements marshal.Marshallable.CopyIn.
-func (ke *KernelIPTGetEntries) CopyIn(cc marshal.CopyContext, addr usermem.Addr) (int, error) {
-	buf := cc.CopyScratchBuffer(ke.SizeBytes()) // escapes: okay.
-	length, err := cc.CopyInBytes(addr, buf)    // escapes: okay.
-	// Unmarshal unconditionally. If we had a short copy-in, this results in a
-	// partially unmarshalled struct.
-	ke.UnmarshalBytes(buf) // escapes: fallback.
-	return length, err
-}
-
-// CopyOut implements marshal.Marshallable.CopyOut.
-func (ke *KernelIPTGetEntries) CopyOut(cc marshal.CopyContext, addr usermem.Addr) (int, error) {
-	// Type KernelIPTGetEntries doesn't have a packed layout in memory, fall
-	// back to MarshalBytes.
-	return cc.CopyOutBytes(addr, ke.marshalAll(cc))
-}
-
-// CopyOutN implements marshal.Marshallable.CopyOutN.
-func (ke *KernelIPTGetEntries) CopyOutN(cc marshal.CopyContext, addr usermem.Addr, limit int) (int, error) {
-	// Type KernelIPTGetEntries doesn't have a packed layout in memory, fall
-	// back to MarshalBytes.
-	return cc.CopyOutBytes(addr, ke.marshalAll(cc)[:limit])
-}
-
-func (ke *KernelIPTGetEntries) marshalAll(cc marshal.CopyContext) []byte {
-	buf := cc.CopyScratchBuffer(ke.SizeBytes())
-	ke.MarshalBytes(buf)
-	return buf
-}
-
-// WriteTo implements io.WriterTo.WriteTo.
-func (ke *KernelIPTGetEntries) WriteTo(w io.Writer) (int64, error) {
-	buf := make([]byte, ke.SizeBytes())
-	ke.MarshalBytes(buf)
-	length, err := w.Write(buf)
-	return int64(length), err
-}
-
 var _ marshal.Marshallable = (*KernelIPTGetEntries)(nil)
 
 // IPTReplace is the argument for the IPT_SO_SET_REPLACE sockopt. It
diff --git a/pkg/abi/linux/netfilter_ipv6.go b/pkg/abi/linux/netfilter_ipv6.go
index bcb57642e..b953e62dc 100644
--- a/pkg/abi/linux/netfilter_ipv6.go
+++ b/pkg/abi/linux/netfilter_ipv6.go
@@ -15,11 +15,8 @@
 package linux
 
 import (
-	"io"
-
 	"gvisor.dev/gvisor/pkg/marshal"
 	"gvisor.dev/gvisor/pkg/marshal/primitive"
-	"gvisor.dev/gvisor/pkg/usermem"
 )
 
 // This file contains structures required to support IPv6 netfilter and
@@ -70,8 +67,9 @@ type IP6TReplace struct {
 const SizeOfIP6TReplace = 96
 
 // KernelIP6TGetEntries is identical to IP6TGetEntries, but includes the
-// Entrytable field. This has been manually made marshal.Marshallable since it
-// is dynamically sized.
+// Entrytable field.
+//
+// +marshal dynamic
 type KernelIP6TGetEntries struct {
 	IPTGetEntries
 	Entrytable []KernelIP6TEntry
@@ -106,65 +104,6 @@ func (ke *KernelIP6TGetEntries) UnmarshalBytes(src []byte) {
 	}
 }
 
-// Packed implements marshal.Marshallable.Packed.
-func (ke *KernelIP6TGetEntries) Packed() bool {
-	// KernelIP6TGetEntries isn't packed because the ke.Entrytable contains
-	// an indirection to the actual data we want to marshal (the slice data
-	// pointer), and the memory for KernelIP6TGetEntries contains the slice
-	// header which we don't want to marshal.
-	return false
-}
-
-// MarshalUnsafe implements marshal.Marshallable.MarshalUnsafe.
-func (ke *KernelIP6TGetEntries) MarshalUnsafe(dst []byte) {
-	// Fall back to safe Marshal because the type in not packed.
-	ke.MarshalBytes(dst)
-}
-
-// UnmarshalUnsafe implements marshal.Marshallable.UnmarshalUnsafe.
-func (ke *KernelIP6TGetEntries) UnmarshalUnsafe(src []byte) {
-	// Fall back to safe Unmarshal because the type in not packed.
-	ke.UnmarshalBytes(src)
-}
-
-// CopyIn implements marshal.Marshallable.CopyIn.
-func (ke *KernelIP6TGetEntries) CopyIn(cc marshal.CopyContext, addr usermem.Addr) (int, error) {
-	buf := cc.CopyScratchBuffer(ke.SizeBytes()) // escapes: okay.
-	length, err := cc.CopyInBytes(addr, buf)    // escapes: okay.
-	// Unmarshal unconditionally. If we had a short copy-in, this results
-	// in a partially unmarshalled struct.
-	ke.UnmarshalBytes(buf) // escapes: fallback.
-	return length, err
-}
-
-// CopyOut implements marshal.Marshallable.CopyOut.
-func (ke *KernelIP6TGetEntries) CopyOut(cc marshal.CopyContext, addr usermem.Addr) (int, error) {
-	// Type KernelIP6TGetEntries doesn't have a packed layout in memory,
-	// fall back to MarshalBytes.
-	return cc.CopyOutBytes(addr, ke.marshalAll(cc))
-}
-
-// CopyOutN implements marshal.Marshallable.CopyOutN.
-func (ke *KernelIP6TGetEntries) CopyOutN(cc marshal.CopyContext, addr usermem.Addr, limit int) (int, error) {
-	// Type KernelIP6TGetEntries doesn't have a packed layout in memory, fall
-	// back to MarshalBytes.
-	return cc.CopyOutBytes(addr, ke.marshalAll(cc)[:limit])
-}
-
-func (ke *KernelIP6TGetEntries) marshalAll(cc marshal.CopyContext) []byte {
-	buf := cc.CopyScratchBuffer(ke.SizeBytes())
-	ke.MarshalBytes(buf)
-	return buf
-}
-
-// WriteTo implements io.WriterTo.WriteTo.
-func (ke *KernelIP6TGetEntries) WriteTo(w io.Writer) (int64, error) {
-	buf := make([]byte, ke.SizeBytes())
-	ke.MarshalBytes(buf)
-	length, err := w.Write(buf)
-	return int64(length), err
-}
-
 var _ marshal.Marshallable = (*KernelIP6TGetEntries)(nil)
 
 // IP6TEntry is an iptables rule. It corresponds to struct ip6t_entry in