gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/pkg/sentry/socket/unix/transport/host_unsafe.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package transport
    16  
    17  import (
    18  	"unsafe"
    19  
    20  	"golang.org/x/sys/unix"
    21  )
    22  
    23  // fdReadVec receives from fd to bufs.
    24  //
    25  // If the total length of bufs is > maxlen, fdReadVec will do a partial read
    26  // and err will indicate why the message was truncated.
    27  func fdReadVec(fd int, bufs [][]byte, control []byte, peek bool, maxlen int64) (readLen int64, msgLen int64, controlLen uint64, controlTrunc bool, err error) {
    28  	flags := uintptr(unix.MSG_DONTWAIT | unix.MSG_TRUNC)
    29  	if peek {
    30  		flags |= unix.MSG_PEEK
    31  	}
    32  
    33  	// Always truncate the receive buffer. All socket types will truncate
    34  	// received messages.
    35  	length, iovecs, intermediate, err := buildIovec(bufs, maxlen, true)
    36  	if err != nil && len(iovecs) == 0 {
    37  		// No partial write to do, return error immediately.
    38  		return 0, 0, 0, false, err
    39  	}
    40  
    41  	var msg unix.Msghdr
    42  	if len(control) != 0 {
    43  		msg.Control = &control[0]
    44  		msg.Controllen = uint64(len(control))
    45  	}
    46  
    47  	if len(iovecs) != 0 {
    48  		msg.Iov = &iovecs[0]
    49  		msg.Iovlen = uint64(len(iovecs))
    50  	}
    51  
    52  	rawN, _, e := unix.RawSyscall(unix.SYS_RECVMSG, uintptr(fd), uintptr(unsafe.Pointer(&msg)), flags)
    53  	if e != 0 {
    54  		// N.B. prioritize the syscall error over the buildIovec error.
    55  		return 0, 0, 0, false, e
    56  	}
    57  	n := int64(rawN)
    58  
    59  	// Copy data back to bufs.
    60  	if intermediate != nil {
    61  		copyToMulti(bufs, intermediate)
    62  	}
    63  
    64  	controlTrunc = msg.Flags&unix.MSG_CTRUNC == unix.MSG_CTRUNC
    65  
    66  	if n > length {
    67  		return length, n, msg.Controllen, controlTrunc, nil
    68  	}
    69  
    70  	return n, n, msg.Controllen, controlTrunc, nil
    71  }
    72  
    73  // fdWriteVec sends from bufs to fd.
    74  //
    75  // If the total length of bufs is > maxlen && truncate, fdWriteVec will do a
    76  // partial write and err will indicate why the message was truncated.
    77  func fdWriteVec(fd int, bufs [][]byte, maxlen int64, truncate bool) (int64, int64, error) {
    78  	length, iovecs, intermediate, err := buildIovec(bufs, maxlen, truncate)
    79  	if err != nil && len(iovecs) == 0 {
    80  		// No partial write to do, return error immediately.
    81  		return 0, length, err
    82  	}
    83  
    84  	// Copy data to intermediate buf.
    85  	if intermediate != nil {
    86  		copyFromMulti(intermediate, bufs)
    87  	}
    88  
    89  	var msg unix.Msghdr
    90  	if len(iovecs) > 0 {
    91  		msg.Iov = &iovecs[0]
    92  		msg.Iovlen = uint64(len(iovecs))
    93  	}
    94  
    95  	n, _, e := unix.RawSyscall(unix.SYS_SENDMSG, uintptr(fd), uintptr(unsafe.Pointer(&msg)), unix.MSG_DONTWAIT|unix.MSG_NOSIGNAL)
    96  	if e != 0 {
    97  		// N.B. prioritize the syscall error over the buildIovec error.
    98  		return 0, length, e
    99  	}
   100  
   101  	return int64(n), length, err
   102  }