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91b8f208a2
By using main instead of the v1.1 branch, we drop an unnecessary dependency on cilium/ebpf, saving ~1mb of binary size. Signed-off-by: Matt Heon <mheon@redhat.com>
120 lines
3.5 KiB
Go
120 lines
3.5 KiB
Go
package utils
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/*
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* Copyright 2016, 2017 SUSE LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import (
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"fmt"
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"os"
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"runtime"
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"golang.org/x/sys/unix"
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)
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// MaxNameLen is the maximum length of the name of a file descriptor being sent
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// using SendFile. The name of the file handle returned by RecvFile will never be
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// larger than this value.
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const MaxNameLen = 4096
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// oobSpace is the size of the oob slice required to store a single FD. Note
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// that unix.UnixRights appears to make the assumption that fd is always int32,
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// so sizeof(fd) = 4.
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var oobSpace = unix.CmsgSpace(4)
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// RecvFile waits for a file descriptor to be sent over the given AF_UNIX
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// socket. The file name of the remote file descriptor will be recreated
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// locally (it is sent as non-auxiliary data in the same payload).
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func RecvFile(socket *os.File) (_ *os.File, Err error) {
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name := make([]byte, MaxNameLen)
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oob := make([]byte, oobSpace)
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sockfd := socket.Fd()
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n, oobn, _, _, err := unix.Recvmsg(int(sockfd), name, oob, unix.MSG_CMSG_CLOEXEC)
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if err != nil {
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return nil, err
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}
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if n >= MaxNameLen || oobn != oobSpace {
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return nil, fmt.Errorf("recvfile: incorrect number of bytes read (n=%d oobn=%d)", n, oobn)
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}
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// Truncate.
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name = name[:n]
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oob = oob[:oobn]
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scms, err := unix.ParseSocketControlMessage(oob)
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if err != nil {
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return nil, err
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}
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// We cannot control how many SCM_RIGHTS we receive, and upon receiving
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// them all of the descriptors are installed in our fd table, so we need to
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// parse all of the SCM_RIGHTS we received in order to close all of the
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// descriptors on error.
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var fds []int
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defer func() {
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for i, fd := range fds {
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if i == 0 && Err == nil {
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// Only close the first one on error.
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continue
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}
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// Always close extra ones.
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_ = unix.Close(fd)
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}
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}()
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var lastErr error
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for _, scm := range scms {
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if scm.Header.Type == unix.SCM_RIGHTS {
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scmFds, err := unix.ParseUnixRights(&scm)
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if err != nil {
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lastErr = err
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} else {
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fds = append(fds, scmFds...)
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}
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}
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}
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if lastErr != nil {
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return nil, lastErr
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}
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// We do this after collecting the fds to make sure we close them all when
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// returning an error here.
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if len(scms) != 1 {
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return nil, fmt.Errorf("recvfd: number of SCMs is not 1: %d", len(scms))
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}
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if len(fds) != 1 {
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return nil, fmt.Errorf("recvfd: number of fds is not 1: %d", len(fds))
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}
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return os.NewFile(uintptr(fds[0]), string(name)), nil
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}
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// SendFile sends a file over the given AF_UNIX socket. file.Name() is also
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// included so that if the other end uses RecvFile, the file will have the same
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// name information.
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func SendFile(socket *os.File, file *os.File) error {
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name := file.Name()
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if len(name) >= MaxNameLen {
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return fmt.Errorf("sendfd: filename too long: %s", name)
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}
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err := SendRawFd(socket, name, file.Fd())
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runtime.KeepAlive(file)
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return err
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}
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// SendRawFd sends a specific file descriptor over the given AF_UNIX socket.
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func SendRawFd(socket *os.File, msg string, fd uintptr) error {
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oob := unix.UnixRights(int(fd))
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return unix.Sendmsg(int(socket.Fd()), []byte(msg), oob, nil, 0)
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}
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