sys/linux: extend netfilter descriptions

1 files changed, 71 insertions, 0 deletions

diff --git a/sys/linux/init_iptables.go b/sys/linux/init_iptables.go
new file mode 100644
index 000000000..1a5a1ccc9
--- /dev/null
+++ b/sys/linux/init_iptables.go
@@ -0,0 +1,71 @@
+// Copyright 2018 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package linux
+
+import (
+	"strings"
+
+	"github.com/google/syzkaller/prog"
+)
+
+func (arch *arch) generateIptables(g *prog.Gen, typ prog.Type, old prog.Arg) (
+	arg prog.Arg, calls []*prog.Call) {
+	if old == nil {
+		arg = g.GenerateSpecialArg(typ, &calls)
+	} else {
+		arg = old
+		calls = g.MutateArg(arg)
+	}
+	tableArg := arg.(*prog.UnionArg).Option.(*prog.GroupArg)
+	if len(tableArg.Inner) != 17 {
+		panic("iptable is expected to have 17 fields")
+	}
+	entriesArg := tableArg.Inner[16].(*prog.GroupArg)
+	if len(entriesArg.Inner) != 2 {
+		panic("iptable entries is expected to have 2 fields")
+	}
+	underflowArg := entriesArg.Inner[0].(*prog.GroupArg)
+	entriesArray := entriesArg.Inner[1].(*prog.GroupArg)
+	// Collect offsets of entries.
+	offsets := make([]uint64, len(entriesArray.Inner))
+	pos := underflowArg.Size()
+	for i, entryArg := range entriesArray.Inner {
+		offsets[i] = pos
+		pos += entryArg.Size()
+	}
+	genOffset := func() uint64 {
+		if g.Rand().Intn(100) == 0 {
+			// Assign the underflow entry once in a while.
+			// We have it in underflow hooks, so no point in using it frequently.
+			return 0
+		} else {
+			return offsets[g.Rand().Intn(len(offsets))]
+		}
+	}
+	// Assign offsets to used hooks.
+	for hook := 4; hook < 9; hook++ {
+		hookArg := tableArg.Inner[hook].(*prog.ConstArg)
+		if hookArg.Type().(*prog.ConstType).Val == uint64(^uint32(0)) {
+			continue // unused hook
+		}
+		hookArg.Val = genOffset()
+	}
+	// Now update standard target jump offsets.
+	prog.ForeachSubarg(arg, func(arg, _ prog.Arg, _ *[]prog.Arg) {
+		if !strings.HasPrefix(arg.Type().Name(), `xt_target_t["", `) {
+			return
+		}
+		targetArg := arg.(*prog.GroupArg)
+		valArg := targetArg.Inner[3].(*prog.ConstArg)
+		if flagsType, ok := valArg.Type().(*prog.FlagsType); ok && int64(valArg.Val) < 0 {
+			for _, val := range flagsType.Vals {
+				if val == valArg.Val {
+					return // verdict
+				}
+			}
+		}
+		valArg.Val = genOffset()
+	})
+	return
+}