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// Copyright 2014 The Chromium 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 "mojo/edk/embedder/platform_channel_utils_posix.h"
#include <sys/socket.h>
#include <sys/uio.h>
#include <unistd.h>
#include "base/logging.h"
#include "base/posix/eintr_wrapper.h"
#include "build/build_config.h"
namespace mojo {
namespace edk {
// On Linux, |SIGPIPE| is suppressed by passing |MSG_NOSIGNAL| to
// |send()|/|sendmsg()|. (There is no way of suppressing |SIGPIPE| on
// |write()|/|writev().) On Mac, |SIGPIPE| is suppressed by setting the
// |SO_NOSIGPIPE| option on the socket.
//
// Performance notes:
// - On Linux, we have to use |send()|/|sendmsg()| rather than
// |write()|/|writev()| in order to suppress |SIGPIPE|. This is okay, since
// |send()| is (slightly) faster than |write()| (!), while |sendmsg()| is
// quite comparable to |writev()|.
// - On Mac, we may use |write()|/|writev()|. Here, |write()| is considerably
// faster than |send()|, whereas |sendmsg()| is quite comparable to
// |writev()|.
// - On both platforms, an appropriate |sendmsg()|/|writev()| is considerably
// faster than two |send()|s/|write()|s.
// - Relative numbers (minimum real times from 10 runs) for one |write()| of
// 1032 bytes, one |send()| of 1032 bytes, one |writev()| of 32+1000 bytes,
// one |sendmsg()| of 32+1000 bytes, two |write()|s of 32 and 1000 bytes, two
// |send()|s of 32 and 1000 bytes:
// - Linux: 0.81 s, 0.77 s, 0.87 s, 0.89 s, 1.31 s, 1.22 s
// - Mac: 2.21 s, 2.91 s, 2.98 s, 3.08 s, 3.59 s, 4.74 s
// Flags to use with calling |send()| or |sendmsg()| (see above).
#if defined(OS_MACOSX)
const int kSendFlags = 0;
#else
const int kSendFlags = MSG_NOSIGNAL;
#endif
ssize_t PlatformChannelWrite(PlatformHandle h,
const void* bytes,
size_t num_bytes) {
DCHECK(h.is_valid());
DCHECK(bytes);
DCHECK_GT(num_bytes, 0u);
#if defined(OS_MACOSX)
return HANDLE_EINTR(write(h.fd, bytes, num_bytes));
#else
return send(h.fd, bytes, num_bytes, kSendFlags);
#endif
}
ssize_t PlatformChannelWritev(PlatformHandle h,
struct iovec* iov,
size_t num_iov) {
DCHECK(h.is_valid());
DCHECK(iov);
DCHECK_GT(num_iov, 0u);
#if defined(OS_MACOSX)
return HANDLE_EINTR(writev(h.fd, iov, static_cast<int>(num_iov)));
#else
struct msghdr msg = {};
msg.msg_iov = iov;
msg.msg_iovlen = num_iov;
return HANDLE_EINTR(sendmsg(h.fd, &msg, kSendFlags));
#endif
}
ssize_t PlatformChannelSendmsgWithHandles(PlatformHandle h,
struct iovec* iov,
size_t num_iov,
PlatformHandle* platform_handles,
size_t num_platform_handles) {
DCHECK(iov);
DCHECK_GT(num_iov, 0u);
DCHECK(platform_handles);
DCHECK_GT(num_platform_handles, 0u);
DCHECK_LE(num_platform_handles, kPlatformChannelMaxNumHandles);
char cmsg_buf[CMSG_SPACE(kPlatformChannelMaxNumHandles * sizeof(int))];
struct msghdr msg = {};
msg.msg_iov = iov;
msg.msg_iovlen = num_iov;
msg.msg_control = cmsg_buf;
msg.msg_controllen = CMSG_LEN(num_platform_handles * sizeof(int));
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(num_platform_handles * sizeof(int));
for (size_t i = 0; i < num_platform_handles; i++) {
DCHECK(platform_handles[i].is_valid());
reinterpret_cast<int*>(CMSG_DATA(cmsg))[i] = platform_handles[i].fd;
}
return HANDLE_EINTR(sendmsg(h.fd, &msg, kSendFlags));
}
bool PlatformChannelSendHandles(PlatformHandle h,
PlatformHandle* handles,
size_t num_handles) {
DCHECK(handles);
DCHECK_GT(num_handles, 0u);
DCHECK_LE(num_handles, kPlatformChannelMaxNumHandles);
// Note: |sendmsg()| fails on Mac if we don't write at least one character.
struct iovec iov = {const_cast<char*>(""), 1};
char cmsg_buf[CMSG_SPACE(kPlatformChannelMaxNumHandles * sizeof(int))];
struct msghdr msg = {};
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cmsg_buf;
msg.msg_controllen = CMSG_LEN(num_handles * sizeof(int));
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(num_handles * sizeof(int));
for (size_t i = 0; i < num_handles; i++) {
DCHECK(handles[i].is_valid());
reinterpret_cast<int*>(CMSG_DATA(cmsg))[i] = handles[i].fd;
}
ssize_t result = HANDLE_EINTR(sendmsg(h.fd, &msg, kSendFlags));
if (result < 1) {
DCHECK_EQ(result, -1);
return false;
}
for (size_t i = 0; i < num_handles; i++)
handles[i].CloseIfNecessary();
return true;
}
ssize_t PlatformChannelRecvmsg(PlatformHandle h,
void* buf,
size_t num_bytes,
std::deque<PlatformHandle>* platform_handles) {
DCHECK(buf);
DCHECK_GT(num_bytes, 0u);
DCHECK(platform_handles);
struct iovec iov = {buf, num_bytes};
char cmsg_buf[CMSG_SPACE(kPlatformChannelMaxNumHandles * sizeof(int))];
struct msghdr msg = {};
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cmsg_buf;
msg.msg_controllen = sizeof(cmsg_buf);
ssize_t result = HANDLE_EINTR(recvmsg(h.fd, &msg, MSG_DONTWAIT));
if (result < 0)
return result;
// Success; no control messages.
if (msg.msg_controllen == 0)
return result;
DCHECK(!(msg.msg_flags & MSG_CTRUNC));
for (cmsghdr* cmsg = CMSG_FIRSTHDR(&msg); cmsg;
cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
size_t payload_length = cmsg->cmsg_len - CMSG_LEN(0);
DCHECK_EQ(payload_length % sizeof(int), 0u);
size_t num_fds = payload_length / sizeof(int);
const int* fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
for (size_t i = 0; i < num_fds; i++) {
platform_handles->push_back(PlatformHandle(fds[i]));
DCHECK(platform_handles->back().is_valid());
}
}
}
return result;
}
} // namespace edk
} // namespace mojo
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