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// Copyright (c) 2011 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 "base/posix/unix_domain_socket_linux.h"
#include <errno.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <unistd.h>
#include <vector>
#include "base/files/scoped_file.h"
#include "base/logging.h"
#include "base/memory/scoped_vector.h"
#include "base/pickle.h"
#include "base/posix/eintr_wrapper.h"
#include "base/stl_util.h"
const size_t UnixDomainSocket::kMaxFileDescriptors = 16;
// Creates a connected pair of UNIX-domain SOCK_SEQPACKET sockets, and passes
// ownership of the newly allocated file descriptors to |one| and |two|.
// Returns true on success.
static bool CreateSocketPair(base::ScopedFD* one, base::ScopedFD* two) {
int raw_socks[2];
if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_socks) == -1)
return false;
one->reset(raw_socks[0]);
two->reset(raw_socks[1]);
return true;
}
// static
bool UnixDomainSocket::EnableReceiveProcessId(int fd) {
const int enable = 1;
return setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &enable, sizeof(enable)) == 0;
}
// static
bool UnixDomainSocket::SendMsg(int fd,
const void* buf,
size_t length,
const std::vector<int>& fds) {
struct msghdr msg = {};
struct iovec iov = { const_cast<void*>(buf), length };
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
char* control_buffer = NULL;
if (fds.size()) {
const unsigned control_len = CMSG_SPACE(sizeof(int) * fds.size());
control_buffer = new char[control_len];
struct cmsghdr* cmsg;
msg.msg_control = control_buffer;
msg.msg_controllen = control_len;
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(int) * fds.size());
memcpy(CMSG_DATA(cmsg), &fds[0], sizeof(int) * fds.size());
msg.msg_controllen = cmsg->cmsg_len;
}
// Avoid a SIGPIPE if the other end breaks the connection.
// Due to a bug in the Linux kernel (net/unix/af_unix.c) MSG_NOSIGNAL isn't
// regarded for SOCK_SEQPACKET in the AF_UNIX domain, but it is mandated by
// POSIX.
const int flags = MSG_NOSIGNAL;
const ssize_t r = HANDLE_EINTR(sendmsg(fd, &msg, flags));
const bool ret = static_cast<ssize_t>(length) == r;
delete[] control_buffer;
return ret;
}
// static
ssize_t UnixDomainSocket::RecvMsg(int fd,
void* buf,
size_t length,
ScopedVector<base::ScopedFD>* fds) {
return UnixDomainSocket::RecvMsgWithPid(fd, buf, length, fds, NULL);
}
// static
ssize_t UnixDomainSocket::RecvMsgWithPid(int fd,
void* buf,
size_t length,
ScopedVector<base::ScopedFD>* fds,
base::ProcessId* pid) {
return UnixDomainSocket::RecvMsgWithFlags(fd, buf, length, 0, fds, pid);
}
// static
ssize_t UnixDomainSocket::RecvMsgWithFlags(int fd,
void* buf,
size_t length,
int flags,
ScopedVector<base::ScopedFD>* fds,
base::ProcessId* out_pid) {
fds->clear();
struct msghdr msg = {};
struct iovec iov = { buf, length };
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
char control_buffer[CMSG_SPACE(sizeof(int) * kMaxFileDescriptors) +
CMSG_SPACE(sizeof(struct ucred))];
msg.msg_control = control_buffer;
msg.msg_controllen = sizeof(control_buffer);
const ssize_t r = HANDLE_EINTR(recvmsg(fd, &msg, flags));
if (r == -1)
return -1;
int* wire_fds = NULL;
unsigned wire_fds_len = 0;
base::ProcessId pid = -1;
if (msg.msg_controllen > 0) {
struct cmsghdr* cmsg;
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
const unsigned payload_len = cmsg->cmsg_len - CMSG_LEN(0);
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_RIGHTS) {
DCHECK(payload_len % sizeof(int) == 0);
DCHECK(wire_fds == NULL);
wire_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
wire_fds_len = payload_len / sizeof(int);
}
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS) {
DCHECK(payload_len == sizeof(struct ucred));
DCHECK(pid == -1);
pid = reinterpret_cast<struct ucred*>(CMSG_DATA(cmsg))->pid;
}
}
}
if (msg.msg_flags & MSG_TRUNC || msg.msg_flags & MSG_CTRUNC) {
for (unsigned i = 0; i < wire_fds_len; ++i)
close(wire_fds[i]);
errno = EMSGSIZE;
return -1;
}
if (wire_fds) {
for (unsigned i = 0; i < wire_fds_len; ++i)
fds->push_back(new base::ScopedFD(wire_fds[i]));
}
if (out_pid) {
// |pid| will legitimately be -1 if we read EOF, so only DCHECK if we
// actually received a message. Unfortunately, Linux allows sending zero
// length messages, which are indistinguishable from EOF, so this check
// has false negatives.
if (r > 0 || msg.msg_controllen > 0)
DCHECK_GE(pid, 0);
*out_pid = pid;
}
return r;
}
// static
ssize_t UnixDomainSocket::SendRecvMsg(int fd,
uint8_t* reply,
unsigned max_reply_len,
int* result_fd,
const Pickle& request) {
return UnixDomainSocket::SendRecvMsgWithFlags(fd, reply, max_reply_len,
0, /* recvmsg_flags */
result_fd, request);
}
// static
ssize_t UnixDomainSocket::SendRecvMsgWithFlags(int fd,
uint8_t* reply,
unsigned max_reply_len,
int recvmsg_flags,
int* result_fd,
const Pickle& request) {
// This socketpair is only used for the IPC and is cleaned up before
// returning.
base::ScopedFD recv_sock, send_sock;
if (!CreateSocketPair(&recv_sock, &send_sock))
return -1;
{
std::vector<int> send_fds;
send_fds.push_back(send_sock.get());
if (!SendMsg(fd, request.data(), request.size(), send_fds))
return -1;
}
// Close the sending end of the socket right away so that if our peer closes
// it before sending a response (e.g., from exiting), RecvMsgWithFlags() will
// return EOF instead of hanging.
send_sock.reset();
ScopedVector<base::ScopedFD> recv_fds;
// When porting to OSX keep in mind it doesn't support MSG_NOSIGNAL, so the
// sender might get a SIGPIPE.
const ssize_t reply_len = RecvMsgWithFlags(
recv_sock.get(), reply, max_reply_len, recvmsg_flags, &recv_fds, NULL);
recv_sock.reset();
if (reply_len == -1)
return -1;
// If we received more file descriptors than caller expected, then we treat
// that as an error.
if (recv_fds.size() > (result_fd != NULL ? 1 : 0)) {
NOTREACHED();
return -1;
}
if (result_fd)
*result_fd = recv_fds.empty() ? -1 : recv_fds[0]->release();
return reply_len;
}
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