Real-time collaboration for Jupyter Notebooks, Linux Terminals, LaTeX, VS Code, R IDE, and more,
all in one place.

1
#include <stdio.h>
2
#include <stdlib.h>
3
#include <strings.h>
4
#include <unistd.h>
5
#include <pthread.h>
6

7
#include <sys/mman.h>
8
#include <sys/types.h>
9
#include <sys/socket.h>
10
#include <netinet/ip.h>
11

12
void usage(char* argv0)
13
{
14
    fprintf(stderr, "usage: %s [ -t ] [ -p <port> ]\n", argv0);
15
}
16

17
int read_and_exec(int s)
18
{
19
    int n, length;
20
    int (*payload)(void);
21

22
    fprintf(stderr, "Reading length... ");
23
    if ((n = recv(s, &length, sizeof(length), 0)) != sizeof(length)) {
24
        if (n < 0)
25
            perror("recv");
26
        else
27
            fprintf(stderr, "recv: short read\n");
28
        return -1;
29
    }
30
    fprintf(stderr, "%d\n", length);
31

32
    fprintf(stderr, "Allocating buffer... ");
33
    if ((payload = mmap(NULL, length, PROT_READ | PROT_WRITE | PROT_EXEC,
34
                        MAP_ANON | MAP_PRIVATE, -1, 0)) == (void*)-1) {
35
        perror("mmap");
36
        return -1;
37
    }
38
    fprintf(stderr, "0x%x\n", payload);
39

40
    fprintf(stderr, "Reading payload... ");
41
    if ((n = recv(s, payload, length, 0)) != length) {
42
        if (n < 0)
43
            perror("recv");
44
        else
45
            fprintf(stderr, "recv: short read\n");
46
        return -1;
47
    }
48
    fprintf(stderr, "read %d bytes\n", n);
49

50
    fprintf(stderr, "Executing payload...\n");
51
    
52
    (void*)(*payload)();
53
    
54
    return 0;
55
}
56

57
void* read_and_exec_thread(void* arg)
58
{
59
    return (void*)read_and_exec((int)arg);
60
}
61

62
int create_read_and_exec_thread(int c)
63
{
64
    int err;
65
    pthread_t pthread;
66
    void* return_value;
67
    
68
    if ((err = pthread_create(&pthread, NULL,
69
                              read_and_exec_thread, (void*)c)) != 0) {
70
        fprintf(stderr, "pthread_create: %s\n", strerror(err));
71
        return -1;
72
    }
73

74
    if ((err = pthread_join(pthread, &return_value)) != 0) {
75
        fprintf(stderr, "pthread_join: %s\n", strerror(err));
76
        return -1;
77
    }
78
}
79

80
int main(int argc, char* argv[])
81
{
82
    int c, s, val, threaded = 0;
83
    socklen_t salen;
84
    struct sockaddr_in saddr, client_saddr;
85
    short port = 1234;
86
    
87
    while ((c = getopt(argc, argv, "tp:")) != EOF) {
88
        switch (c) {
89
        case 'p':
90
            port = atoi(optarg);
91
            break;
92
        case 't':
93
            threaded = 1;
94
            break;
95
        default:
96
            usage(argv[0]);
97
            exit(EXIT_FAILURE);
98
        }
99
    }
100

101
    if ((s = socket(AF_INET, SOCK_STREAM, IPPROTO_IP)) < 0) {
102
        perror("socket");
103
        exit(EXIT_FAILURE);
104
    }
105

106
    val = 1;
107
    if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)) < 0) {
108
        perror("setsockopt");
109
        exit(EXIT_FAILURE);
110
    }
111

112
    bzero(&saddr, sizeof(saddr));
113
    saddr.sin_family = AF_INET;
114
    saddr.sin_port = htons(port);
115
    saddr.sin_addr.s_addr = INADDR_ANY;
116
    
117
    if (bind(s, (struct sockaddr*)&saddr, sizeof(saddr)) < 0) {
118
        perror("bind");
119
        exit(EXIT_FAILURE);
120
    }
121

122
    if (listen(s, 5) < 0) {
123
        perror("listen");
124
        exit(EXIT_FAILURE);
125
    }
126

127
    if ((c = accept(s, (struct sockaddr*)&client_saddr, &salen)) < 0) {
128
        perror("accept");
129
        exit(EXIT_FAILURE);
130
    }
131

132
    if (threaded)
133
        exit(create_read_and_exec_thread(c));
134
    else
135
        exit(read_and_exec(c));
136
}
137

138