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/*
* Copyright 2021 Google LLC
* SPDX-License-Identifier: MIT
*/
#include "render_socket.h"
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#define RENDER_SOCKET_MAX_FD_COUNT 8
/* The socket pair between the server process and the client process is set up
* by the client process (or yet another process). Because render_server_run
* does not poll yet, the fd is expected to be blocking.
*
* We also expect the fd to be always valid. If the client process dies, the
* fd becomes invalid and is considered a fatal error.
*
* There is also a socket pair between each context worker and the client
* process. The pair is set up by render_socket_pair here.
*
* The fd is also expected to be blocking. When the client process closes its
* end of the socket pair, the context worker terminates.
*/
bool
render_socket_pair(int out_fds[static 2])
{
int ret = socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0, out_fds);
if (ret) {
render_log("failed to create socket pair");
return false;
}
return true;
}
bool
render_socket_is_seqpacket(int fd)
{
int type;
socklen_t len = sizeof(type);
if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &type, &len))
return false;
return type == SOCK_SEQPACKET;
}
void
render_socket_init(struct render_socket *socket, int fd)
{
assert(fd >= 0);
*socket = (struct render_socket){
.fd = fd,
};
}
void
render_socket_fini(struct render_socket *socket)
{
close(socket->fd);
}
static const int *
get_received_fds(const struct msghdr *msg, int *out_count)
{
const struct cmsghdr *cmsg = CMSG_FIRSTHDR(msg);
if (unlikely(!cmsg || cmsg->cmsg_level != SOL_SOCKET ||
cmsg->cmsg_type != SCM_RIGHTS || cmsg->cmsg_len < CMSG_LEN(0))) {
*out_count = 0;
return NULL;
}
*out_count = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
return (const int *)CMSG_DATA(cmsg);
}
static bool
render_socket_recvmsg(struct render_socket *socket, struct msghdr *msg, size_t *out_size)
{
do {
const ssize_t s = recvmsg(socket->fd, msg, MSG_CMSG_CLOEXEC);
if (unlikely(s <= 0)) {
if (!s)
return false;
if (errno == EAGAIN || errno == EINTR)
continue;
render_log("failed to receive message: %s", strerror(errno));
return false;
}
if (unlikely(msg->msg_flags & (MSG_TRUNC | MSG_CTRUNC))) {
render_log("failed to receive message: truncated");
int fd_count;
const int *fds = get_received_fds(msg, &fd_count);
for (int i = 0; i < fd_count; i++)
close(fds[i]);
return false;
}
*out_size = s;
return true;
} while (true);
}
static bool
render_socket_receive_request_internal(struct render_socket *socket,
void *data,
size_t max_size,
size_t *out_size,
int *fds,
int max_fd_count,
int *out_fd_count)
{
assert(data && max_size);
struct msghdr msg = {
.msg_iov =
&(struct iovec){
.iov_base = data,
.iov_len = max_size,
},
.msg_iovlen = 1,
};
char cmsg_buf[CMSG_SPACE(sizeof(*fds) * RENDER_SOCKET_MAX_FD_COUNT)];
if (max_fd_count) {
assert(fds && max_fd_count <= RENDER_SOCKET_MAX_FD_COUNT);
msg.msg_control = cmsg_buf;
msg.msg_controllen = CMSG_SPACE(sizeof(*fds) * max_fd_count);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
memset(cmsg, 0, sizeof(*cmsg));
}
if (!render_socket_recvmsg(socket, &msg, out_size))
return false;
if (max_fd_count) {
int received_fd_count;
const int *received_fds = get_received_fds(&msg, &received_fd_count);
assert(received_fd_count <= max_fd_count);
memcpy(fds, received_fds, sizeof(*fds) * received_fd_count);
*out_fd_count = received_fd_count;
} else if (out_fd_count) {
*out_fd_count = 0;
}
return true;
}
bool
render_socket_receive_request(struct render_socket *socket,
void *data,
size_t max_size,
size_t *out_size)
{
return render_socket_receive_request_internal(socket, data, max_size, out_size, NULL,
0, NULL);
}
bool
render_socket_receive_request_with_fds(struct render_socket *socket,
void *data,
size_t max_size,
size_t *out_size,
int *fds,
int max_fd_count,
int *out_fd_count)
{
return render_socket_receive_request_internal(socket, data, max_size, out_size, fds,
max_fd_count, out_fd_count);
}
bool
render_socket_receive_data(struct render_socket *socket, void *data, size_t size)
{
size_t received_size;
if (!render_socket_receive_request(socket, data, size, &received_size))
return false;
if (size != received_size) {
render_log("failed to receive data: expected %zu but received %zu", size,
received_size);
return false;
}
return true;
}
static bool
render_socket_sendmsg(struct render_socket *socket, const struct msghdr *msg)
{
do {
const ssize_t s = sendmsg(socket->fd, msg, MSG_NOSIGNAL);
if (unlikely(s < 0)) {
if (errno == EAGAIN || errno == EINTR)
continue;
render_log("failed to send message: %s", strerror(errno));
return false;
}
/* no partial send since the socket type is SOCK_SEQPACKET */
assert(msg->msg_iovlen == 1 && msg->msg_iov[0].iov_len == (size_t)s);
return true;
} while (true);
}
static inline bool
render_socket_send_reply_internal(struct render_socket *socket,
const void *data,
size_t size,
const int *fds,
int fd_count)
{
assert(data && size);
struct msghdr msg = {
.msg_iov =
&(struct iovec){
.iov_base = (void *)data,
.iov_len = size,
},
.msg_iovlen = 1,
};
char cmsg_buf[CMSG_SPACE(sizeof(*fds) * RENDER_SOCKET_MAX_FD_COUNT)];
if (fd_count) {
assert(fds && fd_count <= RENDER_SOCKET_MAX_FD_COUNT);
msg.msg_control = cmsg_buf;
msg.msg_controllen = CMSG_SPACE(sizeof(*fds) * fd_count);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(*fds) * fd_count);
memcpy(CMSG_DATA(cmsg), fds, sizeof(*fds) * fd_count);
}
return render_socket_sendmsg(socket, &msg);
}
bool
render_socket_send_reply(struct render_socket *socket, const void *data, size_t size)
{
return render_socket_send_reply_internal(socket, data, size, NULL, 0);
}
bool
render_socket_send_reply_with_fds(struct render_socket *socket,
const void *data,
size_t size,
const int *fds,
int fd_count)
{
return render_socket_send_reply_internal(socket, data, size, fds, fd_count);
}
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