procfs: Migrate seqfile implementations.

Migrates all (except 3) seqfile implementations to the vfs.DynamicBytesSource
interface. There should not be any change in functionality due to this migration
itself.

Please note that the following seqfile implementations have not been migrated:
- /proc/filesystems in proc/filesystems.go
- /proc/[pid]/mountinfo in proc/mounts.go
- /proc/[pid]/mounts in proc/mounts.go
This is because these depend on pending changes in /pkg/senty/vfs.

PiperOrigin-RevId: 263880719

1 files changed, 338 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/proc/net.go b/pkg/sentry/fsimpl/proc/net.go
new file mode 100644
index 000000000..fd46eebf8
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/net.go
@@ -0,0 +1,338 @@
+// Copyright 2019 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 proc
+
+import (
+	"bytes"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/inet"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/socket"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// ifinet6 implements vfs.DynamicBytesSource for /proc/net/if_inet6.
+//
+// +stateify savable
+type ifinet6 struct {
+	s inet.Stack
+}
+
+var _ vfs.DynamicBytesSource = (*ifinet6)(nil)
+
+func (n *ifinet6) contents() []string {
+	var lines []string
+	nics := n.s.Interfaces()
+	for id, naddrs := range n.s.InterfaceAddrs() {
+		nic, ok := nics[id]
+		if !ok {
+			// NIC was added after NICNames was called. We'll just
+			// ignore it.
+			continue
+		}
+
+		for _, a := range naddrs {
+			// IPv6 only.
+			if a.Family != linux.AF_INET6 {
+				continue
+			}
+
+			// Fields:
+			// IPv6 address displayed in 32 hexadecimal chars without colons
+			// Netlink device number (interface index) in hexadecimal (use nic id)
+			// Prefix length in hexadecimal
+			// Scope value (use 0)
+			// Interface flags
+			// Device name
+			lines = append(lines, fmt.Sprintf("%032x %02x %02x %02x %02x %8s\n", a.Addr, id, a.PrefixLen, 0, a.Flags, nic.Name))
+		}
+	}
+	return lines
+}
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (n *ifinet6) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	for _, l := range n.contents() {
+		buf.WriteString(l)
+	}
+	return nil
+}
+
+// netDev implements vfs.DynamicBytesSource for /proc/net/dev.
+//
+// +stateify savable
+type netDev struct {
+	s inet.Stack
+}
+
+var _ vfs.DynamicBytesSource = (*netDev)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (n *netDev) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	interfaces := n.s.Interfaces()
+	buf.WriteString("Inter-|   Receive                                                |  Transmit\n")
+	buf.WriteString(" face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed\n")
+
+	for _, i := range interfaces {
+		// Implements the same format as
+		// net/core/net-procfs.c:dev_seq_printf_stats.
+		var stats inet.StatDev
+		if err := n.s.Statistics(&stats, i.Name); err != nil {
+			log.Warningf("Failed to retrieve interface statistics for %v: %v", i.Name, err)
+			continue
+		}
+		fmt.Fprintf(
+			buf,
+			"%6s: %7d %7d %4d %4d %4d %5d %10d %9d %8d %7d %4d %4d %4d %5d %7d %10d\n",
+			i.Name,
+			// Received
+			stats[0], // bytes
+			stats[1], // packets
+			stats[2], // errors
+			stats[3], // dropped
+			stats[4], // fifo
+			stats[5], // frame
+			stats[6], // compressed
+			stats[7], // multicast
+			// Transmitted
+			stats[8],  // bytes
+			stats[9],  // packets
+			stats[10], // errors
+			stats[11], // dropped
+			stats[12], // fifo
+			stats[13], // frame
+			stats[14], // compressed
+			stats[15], // multicast
+		)
+	}
+
+	return nil
+}
+
+// netUnix implements vfs.DynamicBytesSource for /proc/net/unix.
+//
+// +stateify savable
+type netUnix struct {
+	k *kernel.Kernel
+}
+
+var _ vfs.DynamicBytesSource = (*netUnix)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (n *netUnix) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	buf.WriteString("Num       RefCount Protocol Flags    Type St Inode Path\n")
+	for _, se := range n.k.ListSockets() {
+		s := se.Sock.Get()
+		if s == nil {
+			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", se.Sock)
+			continue
+		}
+		sfile := s.(*fs.File)
+		if family, _, _ := sfile.FileOperations.(socket.Socket).Type(); family != linux.AF_UNIX {
+			s.DecRef()
+			// Not a unix socket.
+			continue
+		}
+		sops := sfile.FileOperations.(*unix.SocketOperations)
+
+		addr, err := sops.Endpoint().GetLocalAddress()
+		if err != nil {
+			log.Warningf("Failed to retrieve socket name from %+v: %v", sfile, err)
+			addr.Addr = "<unknown>"
+		}
+
+		sockFlags := 0
+		if ce, ok := sops.Endpoint().(transport.ConnectingEndpoint); ok {
+			if ce.Listening() {
+				// For unix domain sockets, linux reports a single flag
+				// value if the socket is listening, of __SO_ACCEPTCON.
+				sockFlags = linux.SO_ACCEPTCON
+			}
+		}
+
+		// In the socket entry below, the value for the 'Num' field requires
+		// some consideration. Linux prints the address to the struct
+		// unix_sock representing a socket in the kernel, but may redact the
+		// value for unprivileged users depending on the kptr_restrict
+		// sysctl.
+		//
+		// One use for this field is to allow a privileged user to
+		// introspect into the kernel memory to determine information about
+		// a socket not available through procfs, such as the socket's peer.
+		//
+		// In gvisor, returning a pointer to our internal structures would
+		// be pointless, as it wouldn't match the memory layout for struct
+		// unix_sock, making introspection difficult. We could populate a
+		// struct unix_sock with the appropriate data, but even that
+		// requires consideration for which kernel version to emulate, as
+		// the definition of this struct changes over time.
+		//
+		// For now, we always redact this pointer.
+		fmt.Fprintf(buf, "%#016p: %08X %08X %08X %04X %02X %5d",
+			(*unix.SocketOperations)(nil), // Num, pointer to kernel socket struct.
+			sfile.ReadRefs()-1,            // RefCount, don't count our own ref.
+			0,                             // Protocol, always 0 for UDS.
+			sockFlags,                     // Flags.
+			sops.Endpoint().Type(),        // Type.
+			sops.State(),                  // State.
+			sfile.InodeID(),               // Inode.
+		)
+
+		// Path
+		if len(addr.Addr) != 0 {
+			if addr.Addr[0] == 0 {
+				// Abstract path.
+				fmt.Fprintf(buf, " @%s", string(addr.Addr[1:]))
+			} else {
+				fmt.Fprintf(buf, " %s", string(addr.Addr))
+			}
+		}
+		fmt.Fprintf(buf, "\n")
+
+		s.DecRef()
+	}
+	return nil
+}
+
+// netTCP implements vfs.DynamicBytesSource for /proc/net/tcp.
+//
+// +stateify savable
+type netTCP struct {
+	k *kernel.Kernel
+}
+
+var _ vfs.DynamicBytesSource = (*netTCP)(nil)
+
+func (n *netTCP) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	t := kernel.TaskFromContext(ctx)
+	buf.WriteString("  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode                                                     \n")
+	for _, se := range n.k.ListSockets() {
+		s := se.Sock.Get()
+		if s == nil {
+			log.Debugf("Couldn't resolve weakref %+v in socket table, racing with destruction?", se.Sock)
+			continue
+		}
+		sfile := s.(*fs.File)
+		sops, ok := sfile.FileOperations.(socket.Socket)
+		if !ok {
+			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", sfile))
+		}
+		if family, stype, _ := sops.Type(); !(family == linux.AF_INET && stype == linux.SOCK_STREAM) {
+			s.DecRef()
+			// Not tcp4 sockets.
+			continue
+		}
+
+		// Linux's documentation for the fields below can be found at
+		// https://www.kernel.org/doc/Documentation/networking/proc_net_tcp.txt.
+		// For Linux's implementation, see net/ipv4/tcp_ipv4.c:get_tcp4_sock().
+		// Note that the header doesn't contain labels for all the fields.
+
+		// Field: sl; entry number.
+		fmt.Fprintf(buf, "%4d: ", se.ID)
+
+		portBuf := make([]byte, 2)
+
+		// Field: local_adddress.
+		var localAddr linux.SockAddrInet
+		if local, _, err := sops.GetSockName(t); err == nil {
+			localAddr = *local.(*linux.SockAddrInet)
+		}
+		binary.LittleEndian.PutUint16(portBuf, localAddr.Port)
+		fmt.Fprintf(buf, "%08X:%04X ",
+			binary.LittleEndian.Uint32(localAddr.Addr[:]),
+			portBuf)
+
+		// Field: rem_address.
+		var remoteAddr linux.SockAddrInet
+		if remote, _, err := sops.GetPeerName(t); err == nil {
+			remoteAddr = *remote.(*linux.SockAddrInet)
+		}
+		binary.LittleEndian.PutUint16(portBuf, remoteAddr.Port)
+		fmt.Fprintf(buf, "%08X:%04X ",
+			binary.LittleEndian.Uint32(remoteAddr.Addr[:]),
+			portBuf)
+
+		// Field: state; socket state.
+		fmt.Fprintf(buf, "%02X ", sops.State())
+
+		// Field: tx_queue, rx_queue; number of packets in the transmit and
+		// receive queue. Unimplemented.
+		fmt.Fprintf(buf, "%08X:%08X ", 0, 0)
+
+		// Field: tr, tm->when; timer active state and number of jiffies
+		// until timer expires. Unimplemented.
+		fmt.Fprintf(buf, "%02X:%08X ", 0, 0)
+
+		// Field: retrnsmt; number of unrecovered RTO timeouts.
+		// Unimplemented.
+		fmt.Fprintf(buf, "%08X ", 0)
+
+		// Field: uid.
+		uattr, err := sfile.Dirent.Inode.UnstableAttr(ctx)
+		if err != nil {
+			log.Warningf("Failed to retrieve unstable attr for socket file: %v", err)
+			fmt.Fprintf(buf, "%5d ", 0)
+		} else {
+			fmt.Fprintf(buf, "%5d ", uint32(uattr.Owner.UID.In(t.UserNamespace()).OrOverflow()))
+		}
+
+		// Field: timeout; number of unanswered 0-window probes.
+		// Unimplemented.
+		fmt.Fprintf(buf, "%8d ", 0)
+
+		// Field: inode.
+		fmt.Fprintf(buf, "%8d ", sfile.InodeID())
+
+		// Field: refcount. Don't count the ref we obtain while deferencing
+		// the weakref to this socket.
+		fmt.Fprintf(buf, "%d ", sfile.ReadRefs()-1)
+
+		// Field: Socket struct address. Redacted due to the same reason as
+		// the 'Num' field in /proc/net/unix, see netUnix.ReadSeqFileData.
+		fmt.Fprintf(buf, "%#016p ", (*socket.Socket)(nil))
+
+		// Field: retransmit timeout. Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: predicted tick of soft clock (delayed ACK control data).
+		// Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: (ack.quick<<1)|ack.pingpong, Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: sending congestion window, Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: Slow start size threshold, -1 if threshold >= 0xFFFF.
+		// Unimplemented, report as large threshold.
+		fmt.Fprintf(buf, "%d", -1)
+
+		fmt.Fprintf(buf, "\n")
+
+		s.DecRef()
+	}
+
+	return nil
+}