Marshallable socket opitons.

Socket option values are now required to implement marshal.Marshallable.

Co-authored-by: Rahat Mahmood <rahat@google.com>
PiperOrigin-RevId: 322831612

3 files changed, 145 insertions, 12 deletions

diff --git a/pkg/abi/linux/BUILD b/pkg/abi/linux/BUILD
index 2b789c4ec..a4bb62013 100644
--- a/pkg/abi/linux/BUILD
+++ b/pkg/abi/linux/BUILD
@@ -72,6 +72,9 @@ go_library(
         "//pkg/abi",
         "//pkg/binary",
         "//pkg/bits",
+        "//pkg/usermem",
+        "//tools/go_marshal/marshal",
+        "//tools/go_marshal/primitive",
     ],
 )
 
diff --git a/pkg/abi/linux/netfilter.go b/pkg/abi/linux/netfilter.go
index 46d8b0b42..a91f9f018 100644
--- a/pkg/abi/linux/netfilter.go
+++ b/pkg/abi/linux/netfilter.go
@@ -14,6 +14,14 @@
 
 package linux
 
+import (
+	"io"
+
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/tools/go_marshal/marshal"
+	"gvisor.dev/gvisor/tools/go_marshal/primitive"
+)
+
 // This file contains structures required to support netfilter, specifically
 // the iptables tool.
 
@@ -76,6 +84,8 @@ const (
 
 // IPTEntry is an iptable rule. It corresponds to struct ipt_entry in
 // include/uapi/linux/netfilter_ipv4/ip_tables.h.
+//
+// +marshal
 type IPTEntry struct {
 	// IP is used to filter packets based on the IP header.
 	IP IPTIP
@@ -112,21 +122,41 @@ type IPTEntry struct {
 // SizeOfIPTEntry is the size of an IPTEntry.
 const SizeOfIPTEntry = 112
 
-// KernelIPTEntry is identical to IPTEntry, but includes the Elems field. This
-// struct marshaled via the binary package to write an IPTEntry to userspace.
+// 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.
 type KernelIPTEntry struct {
-	IPTEntry
+	Entry IPTEntry
 
 	// Elems holds the data for all this rule's matches followed by the
 	// target. It is variable length -- users have to iterate over any
 	// matches and use TargetOffset and NextOffset to make sense of the
 	// data.
-	Elems []byte
+	Elems primitive.ByteSlice
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (ke *KernelIPTEntry) SizeBytes() int {
+	return ke.Entry.SizeBytes() + ke.Elems.SizeBytes()
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (ke *KernelIPTEntry) MarshalBytes(dst []byte) {
+	ke.Entry.MarshalBytes(dst)
+	ke.Elems.MarshalBytes(dst[ke.Entry.SizeBytes():])
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (ke *KernelIPTEntry) UnmarshalBytes(src []byte) {
+	ke.Entry.UnmarshalBytes(src)
+	ke.Elems.UnmarshalBytes(src[ke.Entry.SizeBytes():])
 }
 
 // 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.
+//
+// +marshal
 type IPTIP struct {
 	// Src is the source IP address.
 	Src InetAddr
@@ -189,6 +219,8 @@ const SizeOfIPTIP = 84
 
 // XTCounters holds packet and byte counts for a rule. It corresponds to struct
 // xt_counters in include/uapi/linux/netfilter/x_tables.h.
+//
+// +marshal
 type XTCounters struct {
 	// Pcnt is the packet count.
 	Pcnt uint64
@@ -321,6 +353,8 @@ const SizeOfXTRedirectTarget = 56
 
 // IPTGetinfo is the argument for the IPT_SO_GET_INFO sockopt. It corresponds
 // to struct ipt_getinfo in include/uapi/linux/netfilter_ipv4/ip_tables.h.
+//
+// +marshal
 type IPTGetinfo struct {
 	Name       TableName
 	ValidHooks uint32
@@ -336,6 +370,8 @@ const SizeOfIPTGetinfo = 84
 // IPTGetEntries is the argument for the IPT_SO_GET_ENTRIES sockopt. It
 // corresponds to struct ipt_get_entries in
 // include/uapi/linux/netfilter_ipv4/ip_tables.h.
+//
+// +marshal
 type IPTGetEntries struct {
 	Name TableName
 	Size uint32
@@ -350,13 +386,103 @@ type IPTGetEntries struct {
 const SizeOfIPTGetEntries = 40
 
 // KernelIPTGetEntries is identical to IPTGetEntries, but includes the
-// Entrytable field. This struct marshaled via the binary package to write an
-// KernelIPTGetEntries to userspace.
+// Entrytable field. This has been manually made marshal.Marshallable since it
+// is dynamically sized.
 type KernelIPTGetEntries struct {
 	IPTGetEntries
 	Entrytable []KernelIPTEntry
 }
 
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (ke *KernelIPTGetEntries) SizeBytes() int {
+	res := ke.IPTGetEntries.SizeBytes()
+	for _, entry := range ke.Entrytable {
+		res += entry.SizeBytes()
+	}
+	return res
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (ke *KernelIPTGetEntries) MarshalBytes(dst []byte) {
+	ke.IPTGetEntries.MarshalBytes(dst)
+	marshalledUntil := ke.IPTGetEntries.SizeBytes()
+	for i := 0; i < len(ke.Entrytable); i++ {
+		ke.Entrytable[i].MarshalBytes(dst[marshalledUntil:])
+		marshalledUntil += ke.Entrytable[i].SizeBytes()
+	}
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (ke *KernelIPTGetEntries) UnmarshalBytes(src []byte) {
+	ke.IPTGetEntries.UnmarshalBytes(src)
+	unmarshalledUntil := ke.IPTGetEntries.SizeBytes()
+	for i := 0; i < len(ke.Entrytable); i++ {
+		ke.Entrytable[i].UnmarshalBytes(src[unmarshalledUntil:])
+		unmarshalledUntil += ke.Entrytable[i].SizeBytes()
+	}
+}
+
+// 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(task marshal.Task, addr usermem.Addr) (int, error) {
+	buf := task.CopyScratchBuffer(ke.SizeBytes()) // escapes: okay.
+	length, err := task.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(task marshal.Task, addr usermem.Addr) (int, error) {
+	// Type KernelIPTGetEntries doesn't have a packed layout in memory, fall
+	// back to MarshalBytes.
+	return task.CopyOutBytes(addr, ke.marshalAll(task))
+}
+
+// CopyOutN implements marshal.Marshallable.CopyOutN.
+func (ke *KernelIPTGetEntries) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {
+	// Type KernelIPTGetEntries doesn't have a packed layout in memory, fall
+	// back to MarshalBytes.
+	return task.CopyOutBytes(addr, ke.marshalAll(task)[:limit])
+}
+
+func (ke *KernelIPTGetEntries) marshalAll(task marshal.Task) []byte {
+	buf := task.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
 // corresponds to struct ipt_replace in
 // include/uapi/linux/netfilter_ipv4/ip_tables.h.
@@ -374,12 +500,6 @@ type IPTReplace struct {
 	// Entries [0]IPTEntry
 }
 
-// KernelIPTReplace is identical to IPTReplace, but includes the Entries field.
-type KernelIPTReplace struct {
-	IPTReplace
-	Entries [0]IPTEntry
-}
-
 // SizeOfIPTReplace is the size of an IPTReplace.
 const SizeOfIPTReplace = 96
 
@@ -392,6 +512,8 @@ func (en ExtensionName) String() string {
 }
 
 // TableName holds the name of a netfilter table.
+//
+// +marshal
 type TableName [XT_TABLE_MAXNAMELEN]byte
 
 // String implements fmt.Stringer.
diff --git a/pkg/abi/linux/socket.go b/pkg/abi/linux/socket.go
index 95337c168..c24a8216e 100644
--- a/pkg/abi/linux/socket.go
+++ b/pkg/abi/linux/socket.go
@@ -234,6 +234,8 @@ const (
 const SockAddrMax = 128
 
 // InetAddr is struct in_addr, from uapi/linux/in.h.
+//
+// +marshal
 type InetAddr [4]byte
 
 // SockAddrInet is struct sockaddr_in, from uapi/linux/in.h.
@@ -303,6 +305,8 @@ func (s *SockAddrUnix) implementsSockAddr()    {}
 func (s *SockAddrNetlink) implementsSockAddr() {}
 
 // Linger is struct linger, from include/linux/socket.h.
+//
+// +marshal
 type Linger struct {
 	OnOff  int32
 	Linger int32
@@ -317,6 +321,8 @@ const SizeOfLinger = 8
 // the end of this struct or within existing unusued space, so its size grows
 // over time. The current iteration is based on linux v4.17. New versions are
 // always backwards compatible.
+//
+// +marshal
 type TCPInfo struct {
 	State       uint8
 	CaState     uint8
@@ -414,6 +420,8 @@ var SizeOfControlMessageHeader = int(binary.Size(ControlMessageHeader{}))
 // A ControlMessageCredentials is an SCM_CREDENTIALS socket control message.
 //
 // ControlMessageCredentials represents struct ucred from linux/socket.h.
+//
+// +marshal
 type ControlMessageCredentials struct {
 	PID int32
 	UID uint32