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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef NETD_SERVER_NETLINK_UTIL_H
     18 #define NETD_SERVER_NETLINK_UTIL_H
     19 
     20 #include <functional>
     21 #include <linux/netlink.h>
     22 #include <linux/rtnetlink.h>
     23 
     24 #include "NetdConstants.h"
     25 
     26 namespace android {
     27 namespace net {
     28 
     29 const sockaddr_nl KERNEL_NLADDR = {AF_NETLINK, 0, 0, 0};
     30 
     31 const uint16_t NETLINK_REQUEST_FLAGS = NLM_F_REQUEST | NLM_F_ACK;
     32 const uint16_t NETLINK_CREATE_REQUEST_FLAGS = NETLINK_REQUEST_FLAGS | NLM_F_CREATE | NLM_F_EXCL;
     33 const uint16_t NETLINK_DUMP_FLAGS = NLM_F_REQUEST | NLM_F_DUMP;
     34 
     35 // Generic code for processing netlink dumps.
     36 const int kNetlinkDumpBufferSize = 8192;
     37 typedef std::function<void(nlmsghdr *)> NetlinkDumpCallback;
     38 typedef std::function<bool(nlmsghdr *)> NetlinkDumpFilter;
     39 
     40 // Opens an RTNetlink socket and connects it to the kernel.
     41 WARN_UNUSED_RESULT int openNetlinkSocket(int protocol);
     42 
     43 // Receives a netlink ACK. Returns 0 if the command succeeded or negative errno if the command
     44 // failed or receiving the ACK failed.
     45 WARN_UNUSED_RESULT int recvNetlinkAck(int sock);
     46 
     47 // Sends a netlink request and possibly expects an ACK. The first element of iov should be null and
     48 // will be set to the netlink message headerheader. The subsequent elements are the contents of the
     49 // request.
     50 
     51 // Disable optimizations in ASan build.
     52 // ASan reports an out-of-bounds 32-bit(!) access in the first loop of the
     53 // function (over iov[]).
     54 #ifdef __clang__
     55 #if __has_feature(address_sanitizer)
     56 __attribute__((optnone))
     57 #endif
     58 #endif
     59 WARN_UNUSED_RESULT int sendNetlinkRequest(uint16_t action, uint16_t flags, iovec* iov, int iovlen,
     60                                           const NetlinkDumpCallback *callback);
     61 
     62 // Processes a netlink dump, passing every message to the specified |callback|.
     63 WARN_UNUSED_RESULT int processNetlinkDump(int sock, const NetlinkDumpCallback& callback);
     64 
     65 // Flushes netlink objects that take an rtmsg structure (FIB rules, routes...). |getAction| and
     66 // |deleteAction| specify the netlink message types, e.g., RTM_GETRULE and RTM_DELRULE.
     67 // |shouldDelete| specifies whether a given object should be deleted or not. |what| is a
     68 // human-readable name for the objects being flushed, e.g. "rules".
     69 WARN_UNUSED_RESULT int rtNetlinkFlush(uint16_t getAction, uint16_t deleteAction,
     70                                       const char *what, const NetlinkDumpFilter& shouldDelete);
     71 
     72 // Returns the value of the specific __u32 attribute, or 0 if the attribute was not present.
     73 uint32_t getRtmU32Attribute(const nlmsghdr *nlh, int attribute);
     74 
     75 }  // namespace net
     76 }  // namespace android
     77 
     78 #endif  // NETD_SERVER_NETLINK_UTIL_H
     79