Home | History | Annotate | Download | only in bionic 
      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include "bionic_netlink.h"
     30 
     31 #include <errno.h>
     32 #include <linux/netlink.h>
     33 #include <linux/rtnetlink.h>
     34 #include <string.h>
     35 #include <stdlib.h>
     36 #include <sys/socket.h>
     37 #include <unistd.h>
     38 
     39 #include "private/ErrnoRestorer.h"
     40 
     41 NetlinkConnection::NetlinkConnection() {
     42   fd_ = -1;
     43 
     44   // The kernel keeps packets under 8KiB (NLMSG_GOODSIZE),
     45   // but that's a bit too large to go on the stack.
     46   size_ = 8192;
     47   data_ = new char[size_];
     48 }
     49 
     50 NetlinkConnection::~NetlinkConnection() {
     51   ErrnoRestorer errno_restorer;
     52   if (fd_ != -1) close(fd_);
     53   delete[] data_;
     54 }
     55 
     56 bool NetlinkConnection::SendRequest(int type) {
     57   // Rather than force all callers to check for the unlikely event of being
     58   // unable to allocate 8KiB, check here.
     59   if (data_ == nullptr) return false;
     60 
     61   // Did we open a netlink socket yet?
     62   if (fd_ == -1) {
     63     fd_ = socket(PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
     64     if (fd_ == -1) return false;
     65   }
     66 
     67   // Construct and send the message.
     68   struct NetlinkMessage {
     69     nlmsghdr hdr;
     70     rtgenmsg msg;
     71   } request;
     72   memset(&request, 0, sizeof(request));
     73   request.hdr.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
     74   request.hdr.nlmsg_type = type;
     75   request.hdr.nlmsg_len = sizeof(request);
     76   request.msg.rtgen_family = AF_UNSPEC; // All families.
     77   return (TEMP_FAILURE_RETRY(send(fd_, &request, sizeof(request), 0)) == sizeof(request));
     78 }
     79 
     80 bool NetlinkConnection::ReadResponses(void callback(void*, nlmsghdr*), void* context) {
     81   // Read through all the responses, handing interesting ones to the callback.
     82   ssize_t bytes_read;
     83   while ((bytes_read = TEMP_FAILURE_RETRY(recv(fd_, data_, size_, 0))) > 0) {
     84     nlmsghdr* hdr = reinterpret_cast<nlmsghdr*>(data_);
     85     for (; NLMSG_OK(hdr, static_cast<size_t>(bytes_read)); hdr = NLMSG_NEXT(hdr, bytes_read)) {
     86       if (hdr->nlmsg_type == NLMSG_DONE) return true;
     87       if (hdr->nlmsg_type == NLMSG_ERROR) {
     88         nlmsgerr* err = reinterpret_cast<nlmsgerr*>(NLMSG_DATA(hdr));
     89         errno = (hdr->nlmsg_len >= NLMSG_LENGTH(sizeof(nlmsgerr))) ? -err->error : EIO;
     90         return false;
     91       }
     92       callback(context, hdr);
     93     }
     94   }
     95 
     96   // We only get here if recv fails before we see a NLMSG_DONE.
     97   return false;
     98 }
     99