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* Copyright (C) 2016 The Android Open Source Project
* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <memory>
#include <vector>
#include <linux/genetlink.h>
#include <linux/netlink.h>
#include <android-base/macros.h>
#include "wificond/net/nl80211_attribute.h"
namespace android {
namespace wificond {
// NL80211Packets are used to communicate with the cfg80211 kernel subsystem
// (via the nl80211 interface). An NL80211 packet is a type of generic netlink
// packet (i.e. it includes netlink and generic netlink headers).
// In order to simplify the design, we also allow this class to represent a
// few types of netlink control messages. In this way the API user is supposed to
// call IsValid() and GetMessageType() in the first place to avoid misuse of
// this class.
class NL80211Packet {
// This is used for creating a NL80211Packet from buffer.
explicit NL80211Packet(const std::vector<uint8_t>& data);
// This is used for creating an empty NL80211Packet to be filled later.
// See comment of SetMessageType() for |type|.
// See comment of SetCommand() for |command|.
// See comment of SetMessageSequence() for |sequence|.
// See comment of SetPortId() for |pid|.
NL80211Packet(uint16_t type,
uint8_t command,
uint32_t sequence,
uint32_t pid);
// We don't copy NL80211Packet for performance reasons.
// However we keep this copy constructor because it makes unit tests easy.
// It prints WARNING log when this copy constructor is called.
NL80211Packet(const NL80211Packet& packet);
// Explicitly specify the move constructor. Otherwise, copy constructor will
// be called on if we move a NL80211Packet object.
NL80211Packet(NL80211Packet&& packet) = default;
~NL80211Packet() = default;
// Returns whether a packet has consistent header fields.
bool IsValid() const;
// Helper functions for Netlink flags.
// Requesting a dump of a kernel obejct.
bool IsDump() const;
// Multipart messages are used to send lists or trees of objects.
// They are supposed to be parsed independently, and must not be reassembled.
// Multipart messages are terminated by NLMSG_DONE, which should be returned
// by GetMessageType().
bool IsMulti() const;
// Getter functions.
uint8_t GetCommand() const;
uint16_t GetFlags() const;
uint16_t GetMessageType() const;
uint32_t GetMessageSequence() const;
uint32_t GetPortId() const;
// Caller is responsible for checking that this is a valid
// NLMSG_ERROR message before calling GetErrorCode().
// Returns an error number defined in errno.h
int GetErrorCode() const;
const std::vector<uint8_t>& GetConstData() const;
// Setter functions.
// In the contexet of nl80211 messages,
// |command| is one of |enum nl80211_commands| in nl80211.h
void SetCommand(uint8_t command);
// |flags| is set of flag bits described by NLM_F_* macros in netlink.h
void AddFlag(uint16_t flag);
void SetFlags(uint16_t flags);
// In the context of nl80211 messages,
// message type is a nl80211 message family id dynamiclly allocated by kernel.
// If this is a control message, it could be one of the following value:
void SetMessageType(uint16_t message_type);
// Requests should carry a sequence number incremented for each request sent.
// For reply message, the sequence number is used to allow referring to a
// previous message with the same sequence number.
void SetMessageSequence(uint32_t message_sequemce);
// Set nlmsg_pid in netlink header.
// nlmsg_pid is the sender process port ID.
// It is *not* associated with a process but a netlink socket.
// We should use sockaddr_nl.nl_pid from sender socket.
// This value should be 0 if message is from kernel.
// See man 7 netlink for details.
void SetPortId(uint32_t pid);
void AddAttribute(const BaseNL80211Attr& attribute);
// For NLA_FLAG attribute
void AddFlagAttribute(int attribute_id);
bool HasAttribute(int id) const;
bool GetAttribute(int id, NL80211NestedAttr* attribute) const;
// Get all attributes to |*attribute| as a vector.
// In case of failure, attributes up until the first invalid attribute
// actually will be present in |attributes|.
bool GetAllAttributes(
std::vector<BaseNL80211Attr>* attributes) const;
template <typename T>
bool GetAttributeValue(int id, T* value) const {
std::vector<uint8_t> empty_vec;
// All data in |attribute| created here will be overwritten by
// GetAttribute(). So we use an empty vector to initialize it,
// regardless of the fact that an empty buffer is not qualified
// for creating a valid attribute.
NL80211Attr<T> attribute(empty_vec);
if (!GetAttribute(id, &attribute)) {
return false;
*value = attribute.GetValue();
return true;
template <typename T>
bool GetAttribute(int id, NL80211Attr<T>* attribute) const {
uint8_t* start = nullptr;
uint8_t* end = nullptr;
if (!BaseNL80211Attr::GetAttributeImpl( + NLMSG_HDRLEN + GENL_HDRLEN,
data_.size() - NLMSG_HDRLEN - GENL_HDRLEN,
id, &start, &end) ||
start == nullptr ||
end == nullptr) {
return false;
*attribute = NL80211Attr<T>(std::vector<uint8_t>(start, end));
if (!attribute->IsValid()) {
return false;
return true;
void DebugLog() const;
std::vector<uint8_t> data_;
} // namespace wificond
} // namespace android
#endif // WIFICOND_NET_NL80211_PACKET_H_