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1 | 1 | package netlink |
2 | 2 |
|
| 3 | +import ( |
| 4 | + "fmt" |
| 5 | + "os" |
| 6 | + "strings" |
| 7 | + "syscall" |
| 8 | + |
| 9 | + "golang.org/x/sys/unix" |
| 10 | +) |
| 11 | + |
3 | 12 | // ideally golang.org/x/sys/unix would define IfReq but it only has |
4 | 13 | // IFNAMSIZ, hence this minimalistic implementation |
5 | 14 | const ( |
6 | 15 | SizeOfIfReq = 40 |
7 | 16 | IFNAMSIZ = 16 |
8 | 17 | ) |
9 | 18 |
|
| 19 | +const TUN = "/dev/net/tun" |
| 20 | + |
10 | 21 | type ifReq struct { |
11 | 22 | Name [IFNAMSIZ]byte |
12 | 23 | Flags uint16 |
13 | 24 | pad [SizeOfIfReq - IFNAMSIZ - 2]byte |
14 | 25 | } |
| 26 | + |
| 27 | +// AddQueues opens and attaches multiple queue file descriptors to an existing |
| 28 | +// TUN/TAP interface in multi-queue mode. |
| 29 | +// |
| 30 | +// It performs TUNSETIFF ioctl on each opened file descriptor with the current |
| 31 | +// tuntap configuration. Each resulting fd is set to non-blocking mode and |
| 32 | +// returned as *os.File. |
| 33 | +// |
| 34 | +// If the interface was created with a name pattern (e.g. "tap%d"), |
| 35 | +// the first successful TUNSETIFF call will return the resolved name, |
| 36 | +// which is saved back into tuntap.Name. |
| 37 | +// |
| 38 | +// This method assumes that the interface already exists and is in multi-queue mode. |
| 39 | +// The returned FDs are also appended to tuntap.Fds and tuntap.Queues is updated. |
| 40 | +// |
| 41 | +// It is the caller's responsibility to close the FDs when they are no longer needed. |
| 42 | +func (tuntap *Tuntap) AddQueues(count int) ([]*os.File, error) { |
| 43 | + if tuntap.Mode < unix.IFF_TUN || tuntap.Mode > unix.IFF_TAP { |
| 44 | + return nil, fmt.Errorf("Tuntap.Mode %v unknown", tuntap.Mode) |
| 45 | + } |
| 46 | + if tuntap.Flags&TUNTAP_MULTI_QUEUE == 0 { |
| 47 | + return nil, fmt.Errorf("TUNTAP_MULTI_QUEUE not set") |
| 48 | + } |
| 49 | + if count < 1 { |
| 50 | + return nil, fmt.Errorf("count must be >= 1") |
| 51 | + } |
| 52 | + |
| 53 | + req, err := unix.NewIfreq(tuntap.Name) |
| 54 | + if err != nil { |
| 55 | + return nil, err |
| 56 | + } |
| 57 | + req.SetUint16(uint16(tuntap.Mode) | uint16(tuntap.Flags)) |
| 58 | + |
| 59 | + var fds []*os.File |
| 60 | + for i := 0; i < count; i++ { |
| 61 | + localReq := req |
| 62 | + fd, err := unix.Open(TUN, os.O_RDWR|syscall.O_CLOEXEC, 0) |
| 63 | + if err != nil { |
| 64 | + cleanupFds(fds) |
| 65 | + return nil, err |
| 66 | + } |
| 67 | + |
| 68 | + err = unix.IoctlIfreq(fd, unix.TUNSETIFF, req) |
| 69 | + if err != nil { |
| 70 | + // close the new fd |
| 71 | + unix.Close(fd) |
| 72 | + // and the already opened ones |
| 73 | + cleanupFds(fds) |
| 74 | + return nil, fmt.Errorf("tuntap IOCTL TUNSETIFF failed [%d]: %w", i, err) |
| 75 | + } |
| 76 | + |
| 77 | + // Set the tun device to non-blocking before use. The below comment |
| 78 | + // taken from: |
| 79 | + // |
| 80 | + // https://github.com/mistsys/tuntap/commit/161418c25003bbee77d085a34af64d189df62bea |
| 81 | + // |
| 82 | + // Note there is a complication because in go, if a device node is |
| 83 | + // opened, go sets it to use nonblocking I/O. However a /dev/net/tun |
| 84 | + // doesn't work with epoll until after the TUNSETIFF ioctl has been |
| 85 | + // done. So we open the unix fd directly, do the ioctl, then put the |
| 86 | + // fd in nonblocking mode, an then finally wrap it in a os.File, |
| 87 | + // which will see the nonblocking mode and add the fd to the |
| 88 | + // pollable set, so later on when we Read() from it blocked the |
| 89 | + // calling thread in the kernel. |
| 90 | + // |
| 91 | + // See |
| 92 | + // https://github.com/golang/go/issues/30426 |
| 93 | + // which got exposed in go 1.13 by the fix to |
| 94 | + // https://github.com/golang/go/issues/30624 |
| 95 | + err = unix.SetNonblock(fd, true) |
| 96 | + if err != nil { |
| 97 | + cleanupFds(fds) |
| 98 | + return nil, fmt.Errorf("tuntap set to non-blocking failed [%d]: %w", i, err) |
| 99 | + } |
| 100 | + |
| 101 | + // create the file from the file descriptor and store it |
| 102 | + file := os.NewFile(uintptr(fd), TUN) |
| 103 | + fds = append(fds, file) |
| 104 | + |
| 105 | + // 1) we only care for the name of the first tap in the multi queue set |
| 106 | + // 2) if the original name was empty, the localReq has now the actual name |
| 107 | + // |
| 108 | + // In addition: |
| 109 | + // This ensures that the link name is always identical to what the kernel returns. |
| 110 | + // Not only in case of an empty name, but also when using name templates. |
| 111 | + // e.g. when the provided name is "tap%d", the kernel replaces %d with the next available number. |
| 112 | + if i == 0 { |
| 113 | + tuntap.Name = strings.Trim(localReq.Name(), "\x00") |
| 114 | + } |
| 115 | + } |
| 116 | + |
| 117 | + tuntap.Fds = append(tuntap.Fds, fds...) |
| 118 | + tuntap.Queues = len(tuntap.Fds) |
| 119 | + return fds, nil |
| 120 | +} |
| 121 | + |
| 122 | +// RemoveQueues closes the given TAP queue file descriptors and removes them |
| 123 | +// from the tuntap.Fds list. |
| 124 | +// |
| 125 | +// This is a logical counterpart to AddQueues and allows releasing specific queues |
| 126 | +// (e.g., to simulate queue failure or perform partial detach). |
| 127 | +// |
| 128 | +// The method updates tuntap.Queues to reflect the number of remaining active queues. |
| 129 | +// |
| 130 | +// It is safe to call with a subset of tuntap.Fds, but the caller must ensure |
| 131 | +// that the passed *os.File descriptors belong to this interface. |
| 132 | +func (tuntap *Tuntap) RemoveQueues(fds ...*os.File) error { |
| 133 | + toClose := make(map[uintptr]struct{}, len(fds)) |
| 134 | + for _, fd := range fds { |
| 135 | + toClose[fd.Fd()] = struct{}{} |
| 136 | + } |
| 137 | + |
| 138 | + var newFds []*os.File |
| 139 | + for _, fd := range tuntap.Fds { |
| 140 | + if _, shouldClose := toClose[fd.Fd()]; shouldClose { |
| 141 | + if err := fd.Close(); err != nil { |
| 142 | + return fmt.Errorf("failed to close queue fd %d: %w", fd.Fd(), err) |
| 143 | + } |
| 144 | + tuntap.Queues-- |
| 145 | + } else { |
| 146 | + newFds = append(newFds, fd) |
| 147 | + } |
| 148 | + } |
| 149 | + tuntap.Fds = newFds |
| 150 | + return nil |
| 151 | +} |
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