Make netstack (//pkg/tcpip) buildable for 32 bit

Doing so involved breaking dependencies between //pkg/tcpip and the rest
of gVisor, which are discouraged anyways.

Tested on the Go branch via:
  gvisor.dev/gvisor/pkg/tcpip/...

Addresses #1446.

PiperOrigin-RevId: 363081778

3 files changed, 30 insertions, 17 deletions

diff --git a/pkg/iovec/BUILD b/pkg/iovec/BUILD
index b92a58556..e0c016fa3 100644
--- a/pkg/iovec/BUILD
+++ b/pkg/iovec/BUILD
@@ -4,12 +4,12 @@ package(licenses = ["notice"])
 
 go_library(
     name = "iovec",
-    srcs = ["iovec.go"],
-    visibility = ["//:sandbox"],
-    deps = [
-        "//pkg/abi/linux",
-        "@org_golang_x_sys//unix:go_default_library",
+    srcs = [
+        "iovec.go",
+        "iovec_max.go",
     ],
+    visibility = ["//:sandbox"],
+    deps = ["@org_golang_x_sys//unix:go_default_library"],
 )
 
 go_test(
diff --git a/pkg/iovec/iovec.go b/pkg/iovec/iovec.go
index 0789c74bf..f6791060f 100644
--- a/pkg/iovec/iovec.go
+++ b/pkg/iovec/iovec.go
@@ -20,12 +20,8 @@ package iovec
 
 import (
 	"golang.org/x/sys/unix"
-	"gvisor.dev/gvisor/pkg/abi/linux"
 )
 
-// MaxIovs is the maximum number of iovecs host platform can accept.
-var MaxIovs = linux.UIO_MAXIOV
-
 // Builder is a builder for slice of unix.Iovec.
 type Builder struct {
 	iovec   []unix.Iovec
@@ -47,10 +43,10 @@ func (b *Builder) Add(buf []byte) {
 		b.addByAppend(buf)
 		return
 	}
-	b.iovec = append(b.iovec, unix.Iovec{
-		Base: &buf[0],
-		Len:  uint64(len(buf)),
-	})
+
+	b.iovec = append(b.iovec, unix.Iovec{Base: &buf[0]})
+	b.iovec[len(b.iovec)-1].SetLen(len(buf))
+
 	// Keep the last buf if iovec is at max capacity. We will need to append to it
 	// for later bufs.
 	if len(b.iovec) == MaxIovs {
@@ -61,10 +57,8 @@ func (b *Builder) Add(buf []byte) {
 
 func (b *Builder) addByAppend(buf []byte) {
 	b.overflow = append(b.overflow, buf...)
-	b.iovec[len(b.iovec)-1] = unix.Iovec{
-		Base: &b.overflow[0],
-		Len:  uint64(len(b.overflow)),
-	}
+	b.iovec[len(b.iovec)-1] = unix.Iovec{Base: &b.overflow[0]}
+	b.iovec[len(b.iovec)-1].SetLen(len(b.overflow))
 }
 
 // Build returns the final Iovec slice. The length of returned iovec will not
diff --git a/pkg/iovec/iovec_max.go b/pkg/iovec/iovec_max.go
new file mode 100644
index 000000000..724b256e8
--- /dev/null
+++ b/pkg/iovec/iovec_max.go
@@ -0,0 +1,19 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iovec
+
+// MaxIovs is the maximum number of iovecs host platform can accept. It
+// corresponds to Linux's UIO_MAXIOV, which is not in the unix package.
+const MaxIovs = 1024