1 | /*
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2 | This is a simple server that users io_uring in blocking mode.
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3 | It demonstrates the bare minimum needed to use io_uring.
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4 | It uses liburing for simplicity.
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5 | */
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6 |
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7 |
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8 | #include <assert.h>
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9 | #include <stdio.h>
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10 | #include <stdlib.h>
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11 | #include <string.h>
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12 |
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13 | #include <unistd.h>
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14 |
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15 | #include <sys/types.h>
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16 | #include <sys/socket.h>
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17 | #include <netinet/in.h>
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18 |
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19 | #include <liburing.h>
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20 |
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21 | struct io_uring ring;
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22 |
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23 | char data[256];
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24 | struct iovec iov = { data, 256 };
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25 | struct msghdr msg = { (void *)"", 0, &iov, 1, NULL, 0, 0 };
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26 | static void async_read(int sock) {
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27 | /* get an sqe and fill in a READ operation */
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28 | struct io_uring_sqe * sqe = io_uring_get_sqe(&ring);
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29 | io_uring_prep_recvmsg(sqe, sock, &msg, 0);
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30 | sqe->user_data = 0;
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31 |
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32 | /* tell the kernel we have an sqe ready for consumption */
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33 | int ret = io_uring_submit(&ring);
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34 | assert(ret == 1);
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35 | }
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36 |
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37 | int main(int argc, char *argv[]) {
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38 | if(argc != 2) {
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39 | printf("usage: %s portnumber\n", argv[0]);
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40 | exit( EXIT_FAILURE );
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41 | }
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42 | int port = atoi(argv[1]);
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43 | if(port < 1) {
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44 | printf("Invalid port : %d (from %s)\n", port, argv[1]);
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45 | exit( EXIT_FAILURE );
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46 | }
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47 |
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48 | int sock = socket(AF_INET, SOCK_STREAM, 0);
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49 | if(sock < 0) {
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50 | perror( "socket" );
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51 | exit( EXIT_FAILURE );
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52 | }
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53 |
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54 | struct sockaddr_in serv_addr;
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55 | memset(&serv_addr, 0, sizeof(serv_addr));
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56 | serv_addr.sin_family = AF_INET;
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57 | serv_addr.sin_addr.s_addr = INADDR_ANY;
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58 | serv_addr.sin_port = htons(port);
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59 |
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60 | int ret = bind(sock, (struct sockaddr *) &serv_addr, sizeof(serv_addr));
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61 | if(ret < 0) {
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62 | perror( "bind" );
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63 | exit( EXIT_FAILURE );
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64 | }
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65 |
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66 |
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67 | listen(sock,1);
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68 |
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69 | struct sockaddr_in cli_addr;
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70 | __socklen_t clilen = sizeof(cli_addr);
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71 | int newsock = accept(sock, (struct sockaddr *) &cli_addr, &clilen);
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72 | if (newsock < 0) {
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73 | perror( "accept" );
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74 | exit( EXIT_FAILURE );
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75 | }
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76 |
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77 | io_uring_queue_init( 16, &ring, 0 );
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78 |
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79 | async_read( newsock );
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80 |
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81 | while(1) {
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82 | struct io_uring_cqe * cqe;
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83 | struct __kernel_timespec ts = { 2, 0 };
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84 | // int ret = io_uring_wait_cqes( &ring, &cqe, 1, &ts, NULL); // Requires Linux 5.4
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85 | int ret = io_uring_wait_cqe( &ring, &cqe );
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86 |
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87 | if( ret < 0 ) {
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88 | printf( "Main Loop Error : %s\n", strerror(-ret) );
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89 | close( sock );
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90 | exit( EXIT_FAILURE );
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91 | }
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92 |
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93 | switch(cqe->user_data) {
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94 | // Read completed
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95 | case 0:
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96 | // If it is the end of file we are done
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97 | if( cqe->res == 0 ) {
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98 | goto END;
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99 | }
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100 |
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101 | if( cqe->res < 0 ) {
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102 | perror( "Main Loop Error" );
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103 | close( sock );
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104 | exit( EXIT_FAILURE );
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105 | }
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106 |
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107 | printf("'%.*s'\n", cqe->res - 1, data);
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108 |
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109 | async_read( newsock );
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110 |
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111 | // otherwise prepare a new read
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112 | break;
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113 | // Wait timed out, time to print
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114 | // Requires Linux 5.4
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115 | case LIBURING_UDATA_TIMEOUT:
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116 | printf(".");
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117 | break;
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118 | // Problem
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119 | default:
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120 | printf("Unexpected user data : %llu", cqe->user_data);
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121 | exit( EXIT_FAILURE );
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122 | }
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123 |
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124 | io_uring_cqe_seen( &ring, cqe );
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125 | }
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126 | END:
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127 |
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128 | io_uring_queue_exit( &ring );
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129 |
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130 | ret = close(newsock);
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131 | if(ret < 0) {
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132 | perror( "close new" );
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133 | exit( EXIT_FAILURE );
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134 | }
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135 |
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136 | ret = close(sock);
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137 | if(ret < 0) {
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138 | perror( "close old" );
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139 | exit( EXIT_FAILURE );
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140 | }
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141 |
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142 | return 0;
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143 | }
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