sys/openbsd: prevent using vio0 as a virtual multicast interface

One of the root causes to reported "lost connection to test machine" is
when the egress network interface is being used as a multicast
interface:

  setsockopt$inet6_MRT6_ADD_MIF(r0, 0x29, 0x66, &(0x7f0000000180)={0x2}, 0xc)

Prevent such syscalls from being generated by limiting the range of
allowed interface indices.

executor/defs.h

@@ -140,7 +140,7 @@
 
 #if GOARCH_amd64
 #define GOARCH "amd64"
-#define SYZ_REVISION "046b8d64999817e17f0813efa9e374d2ee520a81"
+#define SYZ_REVISION "6255253f9674826c8aeacb80503607f3c81dade2"
 #define SYZ_EXECUTOR_USES_FORK_SERVER 1
 #define SYZ_EXECUTOR_USES_SHMEM 1
 #define SYZ_PAGE_SIZE 4096

sys/openbsd/gen/amd64.go

@@ -189,7 +189,7 @@ var structDescs_amd64 = []*KeyedStruct{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "mif6c_mifi", TypeSize: 2}}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "mif6c_flags", FldName: "mif6c_flags", TypeSize: 1}}, Vals: []uint64{1}, BitMask: true},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "vifc_threshold", TypeSize: 1}}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "mif6c_pifi", TypeSize: 2}}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "mif6c_pifi", TypeSize: 2}}, Kind: 2, RangeBegin: 4, RangeEnd: 65535},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "pad", TypeSize: 2}}, IsPad: true},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "vifc_rate_limit", TypeSize: 4}}},
 	}}},
@@ -2970,4 +2970,4 @@ var consts_amd64 = []ConstValue{
 	{Name: "__MAP_NOREPLACE", Value: 2048},
 }
 
-const revision_amd64 = "046b8d64999817e17f0813efa9e374d2ee520a81"
+const revision_amd64 = "6255253f9674826c8aeacb80503607f3c81dade2"

sys/openbsd/socket_inet6.txt

@@ -46,7 +46,9 @@ mif6ctl {
 	mif6c_mifi	int16
 	mif6c_flags	flags[mif6c_flags, int8]
 	vifc_threshold	int8
-	mif6c_pifi	int16
+# Do not allow low interface indices since one of them is likely to be the
+# egress interface vio0 used on GCE instances during fuzzing.
+	mif6c_pifi	int16[4:0xffff]
 	vifc_rate_limit	int32
 }