shill/net/netlink_sock_diag.cc

// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "shill/net/netlink_sock_diag.h"

#include <linux/inet_diag.h>
#include <linux/netlink.h>
#include <linux/sock_diag.h>
#include <sys/socket.h>
#include <sys/utsname.h>

#include <string>
#include <utility>

#include <base/logging.h>
#include <base/memory/ptr_util.h>
#include <base/numerics/safe_conversions.h>
#include <base/strings/string_number_conversions.h>
#include <base/strings/string_split.h>

#include "shill/net/netlink_fd.h"
#include "shill/net/sockets.h"

namespace {

struct SockDiagRequest {
  struct nlmsghdr header;
  struct inet_diag_req_v2 req_opts;
};

SockDiagRequest CreateDumpRequest(uint8_t family,
                                  uint8_t protocol,
                                  int sequence_number) {
  CHECK(family == AF_INET || family == AF_INET6)
      << "Unsupported SOCK_DIAG family " << family;

  SockDiagRequest request;
  request.header.nlmsg_len = sizeof(SockDiagRequest);
  request.header.nlmsg_type = SOCK_DIAG_BY_FAMILY;
  request.header.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
  request.header.nlmsg_seq = sequence_number;
  request.req_opts.sdiag_family = family;
  request.req_opts.sdiag_protocol = protocol;
  request.req_opts.idiag_states = -1;  // all states
  return request;
}

SockDiagRequest CreateDestroyRequest(uint8_t family, uint8_t protocol) {
  SockDiagRequest request;
  request.header.nlmsg_len = sizeof(SockDiagRequest);
  request.header.nlmsg_type = SOCK_DESTROY;
  request.header.nlmsg_flags = NLM_F_REQUEST;
  request.req_opts.sdiag_family = family;
  request.req_opts.sdiag_protocol = protocol;
  request.req_opts.idiag_states = -1;  // all states
  return request;
}

}  // namespace

namespace shill {

NetlinkSockDiag::NetlinkSockDiag(std::unique_ptr<Sockets> sockets,
                                 int file_descriptor)
    : sockets_(std::move(sockets)),
      file_descriptor_(file_descriptor),
      sequence_number_(0) {}

// static
std::unique_ptr<NetlinkSockDiag> NetlinkSockDiag::Create(
    std::unique_ptr<Sockets> sockets) {
  struct utsname un;
  if (uname(&un) < 0) {
    PLOG(ERROR) << "Could not check kernel version";
    return nullptr;
  }

  unsigned major, minor;
  std::vector<std::string> version = base::SplitString(
      un.release, ".", base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
  if (version.size() < 2 || !base::StringToUint(version[0], &major) ||
      !base::StringToUint(version[1], &minor)) {
    LOG(ERROR) << "Error parsing kernel version";
    return nullptr;
  }

  // SOCK_DESTROY has only been backported to 3.14 and above.
  if (major < 3 || (major == 3 && minor < 14)) {
    LOG(ERROR) << "Kernel version " << major << "." << minor
               << " does not support SOCK_DESTROY";
    return nullptr;
  }

  int file_descriptor =
      OpenNetlinkSocketFD(sockets.get(), NETLINK_SOCK_DIAG, 0);
  if (file_descriptor == Sockets::kInvalidFileDescriptor)
    return nullptr;

  VLOG(2) << "Netlink sock_diag socket started";
  return base::WrapUnique(
      new NetlinkSockDiag(std::move(sockets), file_descriptor));
}

NetlinkSockDiag::~NetlinkSockDiag() {
  sockets_->Close(file_descriptor_);
}

bool NetlinkSockDiag::DestroySockets(uint8_t protocol, const IPAddress& saddr) {
  uint8_t family;
  if (saddr.family() == IPAddress::kFamilyIPv4) {
    family = AF_INET;
  } else if (saddr.family() == IPAddress::kFamilyIPv6) {
    family = AF_INET6;
  } else {
    LOG(ERROR) << "Tried to destroy sockets for unsupported family";
    return false;
  }

  std::vector<struct inet_diag_sockid> socks;
  if (!GetSockets(family, protocol, &socks))
    return false;

  SockDiagRequest request = CreateDestroyRequest(family, protocol);
  for (const auto& sockid : socks) {
    VLOG(1) << "Destroying socket (" << family << ", " << protocol << ")";
    request.header.nlmsg_seq = ++sequence_number_;
    request.req_opts.id = sockid;
    if (!memcmp(sockid.idiag_src, saddr.GetConstData(), saddr.GetLength()) ||
        sockets_->Send(file_descriptor_, static_cast<void*>(&request),
                       sizeof(request), 0) < 0) {
      PLOG(ERROR) << "Failed to write request to netlink socket";
      return false;
    }
  }
  return true;
}

bool NetlinkSockDiag::GetSockets(
    uint8_t family,
    uint8_t protocol,
    std::vector<struct inet_diag_sockid>* out_socks) {
  CHECK(out_socks);
  SockDiagRequest request =
      CreateDumpRequest(family, protocol, ++sequence_number_);
  if (sockets_->Send(file_descriptor_, static_cast<void*>(&request),
                     sizeof(request), 0) < 0) {
    PLOG(ERROR) << "Failed to write sock_diag request to netlink socket "
                << "(family: " << family << ", protocol: " << protocol << ")";
    return false;
  }

  return ReadDumpContents(out_socks);
}

bool NetlinkSockDiag::ReadDumpContents(
    std::vector<struct inet_diag_sockid>* out_socks) {
  char buf[8192];

  out_socks->clear();

  for (;;) {
    ssize_t bytes_read = sockets_->RecvFrom(file_descriptor_, buf, sizeof(buf),
                                            0, nullptr, nullptr);
    if (bytes_read < 0) {
      PLOG(ERROR) << "Failed to read from netlink socket";
      return false;
    }

    size_t unsigned_bytes = base::checked_cast<size_t>(bytes_read);

    for (nlmsghdr* nlh = reinterpret_cast<nlmsghdr*>(buf);
         NLMSG_OK(nlh, unsigned_bytes); nlh = NLMSG_NEXT(nlh, unsigned_bytes)) {
      switch (nlh->nlmsg_type) {
        case NLMSG_DONE:
          return true;
        case NLMSG_ERROR: {
          const nlmsgerr* err =
              reinterpret_cast<const nlmsgerr*> NLMSG_DATA(nlh);
          const char* err_msg = "Error parsing sock_diag netlink socket dump";
          if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*err))) {
            LOG(ERROR) << err_msg;
          } else {
            errno = -err->error;
            PLOG(ERROR) << err_msg;
          }
          return false;
        }
        case SOCK_DIAG_BY_FAMILY:
          struct inet_diag_msg current_msg;
          memcpy(&current_msg, NLMSG_DATA(nlh), sizeof(current_msg));
          out_socks->push_back(current_msg.id);
          break;
        default:
          LOG(WARNING) << "Ignoring unexpected netlink message type "
                       << nlh->nlmsg_type;
          break;
      }
    }
  }
}

}  // namespace shill