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bf8bf407ce
Summary: Add a new helper class for working with cmsghdr structs. This updates the PrivHelperConn code to use this new class, and I will also use this in the upcoming code for implementing graceful mount point takeover on edenfs restart. Reviewed By: bolinfest, wez Differential Revision: D6003897 fbshipit-source-id: 634e9d8f1dc73010c9e9336872cf1270a344bdd2
78 lines
2.2 KiB
C++
78 lines
2.2 KiB
C++
/*
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* Copyright (c) 2004-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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*/
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#include "eden/fs/utils/ControlMsg.h"
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#include <folly/Conv.h>
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#include <stdexcept>
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namespace facebook {
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namespace eden {
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constexpr size_t ControlMsg::kMaxFDs;
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ControlMsg ControlMsg::fromMsg(
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const struct msghdr& msg,
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int level,
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int type,
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size_t expectedSize) {
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auto* cmsg = CMSG_FIRSTHDR(&msg);
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if (!cmsg) {
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throw std::runtime_error("no control data attached to msghdr");
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}
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if (cmsg->cmsg_level != level) {
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throw std::runtime_error(folly::to<std::string>(
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"unexpected control data level: ",
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static_cast<int>(cmsg->cmsg_level),
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" != ",
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level));
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}
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if (cmsg->cmsg_type != type) {
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throw std::runtime_error(folly::to<std::string>(
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"unexpected control data type: ",
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static_cast<int>(cmsg->cmsg_type),
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" != ",
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type));
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}
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if (cmsg->cmsg_len < expectedSize) {
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throw std::runtime_error(folly::to<std::string>(
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"unexpected control data length: ",
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cmsg->cmsg_len,
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" < ",
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expectedSize));
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}
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return ControlMsg(cmsg);
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}
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ControlMsgBuffer::ControlMsgBuffer(size_t dataLen, int level, int type)
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: capacity_{CMSG_SPACE(dataLen)}, buffer_{new uint8_t[capacity_]} {
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cmsg_ = reinterpret_cast<struct cmsghdr*>(buffer_.get());
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cmsg_->cmsg_len = CMSG_LEN(dataLen);
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cmsg_->cmsg_level = level;
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cmsg_->cmsg_type = type;
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}
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void ControlMsgBuffer::shrinkDataLength(size_t dataLen) {
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CHECK_LE(CMSG_SPACE(dataLen), capacity_);
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cmsg_->cmsg_len = CMSG_LEN(dataLen);
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// Update capacity_ as well. This is required since we use the capacity_
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// field to set the msg_controllen field in the msghdr. The kernel will
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// reject the sendmsg() call with EINVAL if msg_controllen is larger than
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// required for the specified cmsg_len.
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capacity_ = CMSG_SPACE(dataLen);
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}
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void ControlMsgBuffer::addToMsg(struct msghdr* msg) {
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msg->msg_control = buffer_.get();
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msg->msg_controllen = capacity_;
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}
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} // namespace eden
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} // namespace facebook
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