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webserver_liburing.c
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#include <stdio.h>
#include <netinet/in.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <liburing.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/utsname.h>
#define SERVER_STRING "Server: zerohttpd/0.1\r\n"
#define DEFAULT_SERVER_PORT 8000
#define QUEUE_DEPTH 256
#define READ_SZ 8192
#define EVENT_TYPE_ACCEPT 0
#define EVENT_TYPE_READ 1
#define EVENT_TYPE_WRITE 2
#define MIN_KERNEL_VERSION 5
#define MIN_MAJOR_VERSION 5
struct request {
int event_type;
int iovec_count;
int client_socket;
struct iovec iov[];
};
struct io_uring ring;
const char *unimplemented_content = \
"HTTP/1.0 400 Bad Request\r\n"
"Content-type: text/html\r\n"
"\r\n"
"<html>"
"<head>"
"<title>ZeroHTTPd: Unimplemented</title>"
"</head>"
"<body>"
"<h1>Bad Request (Unimplemented)</h1>"
"<p>Your client sent a request ZeroHTTPd did not understand and it is probably not your fault.</p>"
"</body>"
"</html>";
const char *http_404_content = \
"HTTP/1.0 404 Not Found\r\n"
"Content-type: text/html\r\n"
"\r\n"
"<html>"
"<head>"
"<title>ZeroHTTPd: Not Found</title>"
"</head>"
"<body>"
"<h1>Not Found (404)</h1>"
"<p>Your client is asking for an object that was not found on this server.</p>"
"</body>"
"</html>";
/*
One function that prints the system call and the error details
and then exits with error code 1. Non-zero meaning things didn't go well.
*/
void fatal_error(const char *syscall) {
perror(syscall);
exit(1);
}
int check_kernel_version() {
struct utsname buffer;
char *p;
long ver[16];
int i=0;
if (uname(&buffer) != 0) {
perror("uname");
exit(EXIT_FAILURE);
}
p = buffer.release;
while (*p) {
if (isdigit(*p)) {
ver[i] = strtol(p, &p, 10);
i++;
} else {
p++;
}
}
printf("Minimum kernel version required is: %d.%d\n",
MIN_KERNEL_VERSION, MIN_MAJOR_VERSION);
if (ver[0] >= MIN_KERNEL_VERSION && ver[1] >= MIN_MAJOR_VERSION ) {
printf("Your kernel version is: %ld.%ld\n", ver[0], ver[1]);
return 0;
}
fprintf(stderr, "Error: your kernel version is: %ld.%ld\n",
ver[0], ver[1]);
return 1;
}
void check_for_index_file() {
struct stat st;
int ret = stat("public/index.html", &st);
if(ret < 0 ) {
fprintf(stderr, "ZeroHTTPd needs the \"public\" directory to be "
"present in the current directory.\n");
fatal_error("stat: public/index.html");
}
}
/*
* Utility function to convert a string to lower case.
* */
void strtolower(char *str) {
for (; *str; ++str)
*str = (char)tolower(*str);
}
/*
* Helper function for cleaner looking code.
* */
void *zh_malloc(size_t size) {
void *buf = malloc(size);
if (!buf) {
fprintf(stderr, "Fatal error: unable to allocate memory.\n");
exit(1);
}
return buf;
}
/*
* This function is responsible for setting up the main listening socket used by the
* web server.
* */
int setup_listening_socket(int port) {
int sock;
struct sockaddr_in srv_addr;
sock = socket(PF_INET, SOCK_STREAM, 0);
if (sock == -1)
fatal_error("socket()");
int enable = 1;
if (setsockopt(sock,
SOL_SOCKET, SO_REUSEADDR,
&enable, sizeof(int)) < 0)
fatal_error("setsockopt(SO_REUSEADDR)");
memset(&srv_addr, 0, sizeof(srv_addr));
srv_addr.sin_family = AF_INET;
srv_addr.sin_port = htons(port);
srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
/* We bind to a port and turn this socket into a listening
* socket.
* */
if (bind(sock,
(const struct sockaddr *)&srv_addr,
sizeof(srv_addr)) < 0)
fatal_error("bind()");
if (listen(sock, 10) < 0)
fatal_error("listen()");
return (sock);
}
int add_accept_request(int server_socket, struct sockaddr_in *client_addr,
socklen_t *client_addr_len) {
struct io_uring_sqe *sqe = io_uring_get_sqe(&ring);
io_uring_prep_accept(sqe, server_socket, (struct sockaddr *) client_addr,
client_addr_len, 0);
struct request *req = malloc(sizeof(*req));
req->event_type = EVENT_TYPE_ACCEPT;
io_uring_sqe_set_data(sqe, req);
io_uring_submit(&ring);
return 0;
}
int add_read_request(int client_socket) {
struct io_uring_sqe *sqe = io_uring_get_sqe(&ring);
struct request *req = malloc(sizeof(*req) + sizeof(struct iovec));
req->iov[0].iov_base = malloc(READ_SZ);
req->iov[0].iov_len = READ_SZ;
req->event_type = EVENT_TYPE_READ;
req->client_socket = client_socket;
memset(req->iov[0].iov_base, 0, READ_SZ);
/* Linux kernel 5.5 has support for readv, but not for recv() or read() */
io_uring_prep_readv(sqe, client_socket, &req->iov[0], 1, 0);
io_uring_sqe_set_data(sqe, req);
io_uring_submit(&ring);
return 0;
}
int add_write_request(struct request *req) {
struct io_uring_sqe *sqe = io_uring_get_sqe(&ring);
req->event_type = EVENT_TYPE_WRITE;
io_uring_prep_writev(sqe, req->client_socket, req->iov, req->iovec_count, 0);
io_uring_sqe_set_data(sqe, req);
io_uring_submit(&ring);
return 0;
}
void _send_static_string_content(const char *str, int client_socket) {
struct request *req = zh_malloc(sizeof(*req) + sizeof(struct iovec));
unsigned long slen = strlen(str);
req->iovec_count = 1;
req->client_socket = client_socket;
req->iov[0].iov_base = zh_malloc(slen);
req->iov[0].iov_len = slen;
memcpy(req->iov[0].iov_base, str, slen);
add_write_request(req);
}
/*
* When ZeroHTTPd encounters any other HTTP method other than GET or POST, this function
* is used to inform the client.
* */
void handle_unimplemented_method(int client_socket) {
_send_static_string_content(unimplemented_content, client_socket);
}
/*
* This function is used to send a "HTTP Not Found" code and message to the client in
* case the file requested is not found.
* */
void handle_http_404(int client_socket) {
_send_static_string_content(http_404_content, client_socket);
}
/*
* Once a static file is identified to be served, this function is used to read the file
* and write it over the client socket using Linux's sendfile() system call. This saves us
* the hassle of transferring file buffers from kernel to user space and back.
* */
void copy_file_contents(char *file_path, off_t file_size, struct iovec *iov) {
int fd;
char *buf = zh_malloc(file_size);
fd = open(file_path, O_RDONLY);
if (fd < 0)
fatal_error("read");
/* We should really check for short reads here */
int ret = read(fd, buf, file_size);
if (ret < file_size) {
fprintf(stderr, "Encountered a short read.\n");
}
close(fd);
iov->iov_base = buf;
iov->iov_len = file_size;
}
/*
* Simple function to get the file extension of the file that we are about to serve.
* */
const char *get_filename_ext(const char *filename) {
const char *dot = strrchr(filename, '.');
if (!dot || dot == filename)
return "";
return dot + 1;
}
/*
* Sends the HTTP 200 OK header, the server string, for a few types of files, it can also
* send the content type based on the file extension. It also sends the content length
* header. Finally it send a '\r\n' in a line by itself signalling the end of headers
* and the beginning of any content.
* */
void send_headers(const char *path, off_t len, struct iovec *iov) {
char small_case_path[1024];
char send_buffer[1024];
strcpy(small_case_path, path);
strtolower(small_case_path);
char *str = "HTTP/1.0 200 OK\r\n";
unsigned long slen = strlen(str);
iov[0].iov_base = zh_malloc(slen);
iov[0].iov_len = slen;
memcpy(iov[0].iov_base, str, slen);
slen = strlen(SERVER_STRING);
iov[1].iov_base = zh_malloc(slen);
iov[1].iov_len = slen;
memcpy(iov[1].iov_base, SERVER_STRING, slen);
/*
* Check the file extension for certain common types of files
* on web pages and send the appropriate content-type header.
* Since extensions can be mixed case like JPG, jpg or Jpg,
* we turn the extension into lower case before checking.
* */
const char *file_ext = get_filename_ext(small_case_path);
if (strcmp("jpg", file_ext) == 0)
strcpy(send_buffer, "Content-Type: image/jpeg\r\n");
if (strcmp("jpeg", file_ext) == 0)
strcpy(send_buffer, "Content-Type: image/jpeg\r\n");
if (strcmp("png", file_ext) == 0)
strcpy(send_buffer, "Content-Type: image/png\r\n");
if (strcmp("gif", file_ext) == 0)
strcpy(send_buffer, "Content-Type: image/gif\r\n");
if (strcmp("htm", file_ext) == 0)
strcpy(send_buffer, "Content-Type: text/html\r\n");
if (strcmp("html", file_ext) == 0)
strcpy(send_buffer, "Content-Type: text/html\r\n");
if (strcmp("js", file_ext) == 0)
strcpy(send_buffer, "Content-Type: application/javascript\r\n");
if (strcmp("css", file_ext) == 0)
strcpy(send_buffer, "Content-Type: text/css\r\n");
if (strcmp("txt", file_ext) == 0)
strcpy(send_buffer, "Content-Type: text/plain\r\n");
slen = strlen(send_buffer);
iov[2].iov_base = zh_malloc(slen);
iov[2].iov_len = slen;
memcpy(iov[2].iov_base, send_buffer, slen);
/* Send the content-length header, which is the file size in this case. */
sprintf(send_buffer, "content-length: %ld\r\n", len);
slen = strlen(send_buffer);
iov[3].iov_base = zh_malloc(slen);
iov[3].iov_len = slen;
memcpy(iov[3].iov_base, send_buffer, slen);
/*
* When the browser sees a '\r\n' sequence in a line on its own,
* it understands there are no more headers. Content may follow.
* */
strcpy(send_buffer, "\r\n");
slen = strlen(send_buffer);
iov[4].iov_base = zh_malloc(slen);
iov[4].iov_len = slen;
memcpy(iov[4].iov_base, send_buffer, slen);
}
void handle_get_method(char *path, int client_socket) {
char final_path[1024];
/*
If a path ends in a trailing slash, the client probably wants the index
file inside of that directory.
*/
if (path[strlen(path) - 1] == '/') {
strcpy(final_path, "public");
strcat(final_path, path);
strcat(final_path, "index.html");
}
else {
strcpy(final_path, "public");
strcat(final_path, path);
}
/* The stat() system call will give you information about the file
* like type (regular file, directory, etc), size, etc. */
struct stat path_stat;
if (stat(final_path, &path_stat) == -1) {
printf("404 Not Found: %s (%s)\n", final_path, path);
handle_http_404(client_socket);
}
else {
/* Check if this is a normal/regular file and not a directory or something else */
if (S_ISREG(path_stat.st_mode)) {
struct request *req = zh_malloc(sizeof(*req) + (sizeof(struct iovec) * 6));
req->iovec_count = 6;
req->client_socket = client_socket;
send_headers(final_path, path_stat.st_size, req->iov);
copy_file_contents(final_path, path_stat.st_size, &req->iov[5]);
printf("200 %s %ld bytes\n", final_path, path_stat.st_size);
add_write_request( req);
}
else {
handle_http_404(client_socket);
printf("404 Not Found: %s\n", final_path);
}
}
}
/*
* This function looks at method used and calls the appropriate handler function.
* Since we only implement GET and POST methods, it calls handle_unimplemented_method()
* in case both these don't match. This sends an error to the client.
* */
void handle_http_method(char *method_buffer, int client_socket) {
char *method, *path, *saveptr;
method = strtok_r(method_buffer, " ", &saveptr);
strtolower(method);
path = strtok_r(NULL, " ", &saveptr);
if (strcmp(method, "get") == 0) {
handle_get_method(path, client_socket);
}
else {
handle_unimplemented_method(client_socket);
}
}
int get_line(const char *src, char *dest, int dest_sz) {
for (int i = 0; i < dest_sz; i++) {
dest[i] = src[i];
if (src[i] == '\r' && src[i+1] == '\n') {
dest[i] = '\0';
return 0;
}
}
return 1;
}
int handle_client_request(struct request *req) {
char http_request[1024];
/* Get the first line, which will be the request */
if(get_line(req->iov[0].iov_base, http_request, sizeof(http_request))) {
fprintf(stderr, "Malformed request\n");
exit(1);
}
handle_http_method(http_request, req->client_socket);
return 0;
}
void server_loop(int server_socket) {
struct io_uring_cqe *cqe;
struct sockaddr_in client_addr;
socklen_t client_addr_len = sizeof(client_addr);
add_accept_request(server_socket, &client_addr, &client_addr_len);
while (1) {
int ret = io_uring_wait_cqe(&ring, &cqe);
struct request *req = (struct request *) cqe->user_data;
if (ret < 0)
fatal_error("io_uring_wait_cqe");
if (cqe->res < 0) {
fprintf(stderr, "Async request failed: %s for event: %d\n",
strerror(-cqe->res), req->event_type);
exit(1);
}
switch (req->event_type) {
case EVENT_TYPE_ACCEPT:
add_accept_request(server_socket, &client_addr, &client_addr_len);
add_read_request(cqe->res);
free(req);
break;
case EVENT_TYPE_READ:
if (!cqe->res) {
fprintf(stderr, "Empty request!\n");
break;
}
handle_client_request(req);
free(req->iov[0].iov_base);
free(req);
break;
case EVENT_TYPE_WRITE:
for (int i = 0; i < req->iovec_count; i++) {
free(req->iov[i].iov_base);
}
close(req->client_socket);
free(req);
break;
}
/* Mark this request as processed */
io_uring_cqe_seen(&ring, cqe);
}
}
void sigint_handler(int signo) {
printf("^C pressed. Shutting down.\n");
io_uring_queue_exit(&ring);
exit(0);
}
int main() {
if (check_kernel_version()) {
return EXIT_FAILURE;
}
check_for_index_file();
int server_socket = setup_listening_socket(DEFAULT_SERVER_PORT);
printf("ZeroHTTPd listening on port: %d\n", DEFAULT_SERVER_PORT);
signal(SIGINT, sigint_handler);
io_uring_queue_init(QUEUE_DEPTH, &ring, 0);
server_loop(server_socket);
return 0;
}