wget: move from cpp-cheat

2026-01-23 02:05:57 +01:00 · 2019-09-22 00:00:00 +00:00
parent f7734aecf7
commit b4b2164f29
3 changed files with 116 additions and 3 deletions
--- a/userland/posix/wget.c
+++ b/userland/posix/wget.c
@@ -0,0 +1,99 @@
+/* https://cirosantilli.com/linux-kernel-module-cheat#socket */
+
+#define _XOPEN_SOURCE 700
+#include <arpa/inet.h>
+#include <assert.h>
+#include <netdb.h> /* getprotobyname */
+#include <netinet/in.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+int main(int argc, char** argv) {
+    char buffer[BUFSIZ];
+    enum CONSTEXPR { MAX_REQUEST_LEN = 1024};
+    char request[MAX_REQUEST_LEN];
+    char request_template[] = "GET / HTTP/1.1\r\nHost: %s\r\n\r\n";
+    struct protoent *protoent;
+    char *hostname = "example.com";
+    in_addr_t in_addr;
+    int request_len;
+    int socket_file_descriptor;
+    ssize_t nbytes_total, nbytes_last;
+    struct hostent *hostent;
+    struct sockaddr_in sockaddr_in;
+    unsigned short server_port = 80;
+
+    if (argc > 1)
+        hostname = argv[1];
+    if (argc > 2)
+        server_port = strtoul(argv[2], NULL, 10);
+
+    request_len = snprintf(request, MAX_REQUEST_LEN, request_template, hostname);
+    if (request_len >= MAX_REQUEST_LEN) {
+        fprintf(stderr, "request length large: %d\n", request_len);
+        exit(EXIT_FAILURE);
+    }
+
+    /* Build the socket. */
+    protoent = getprotobyname("tcp");
+    if (protoent == NULL) {
+        perror("getprotobyname");
+        exit(EXIT_FAILURE);
+    }
+    socket_file_descriptor = socket(AF_INET, SOCK_STREAM, protoent->p_proto);
+    if (socket_file_descriptor == -1) {
+        perror("socket");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Build the address. */
+    hostent = gethostbyname(hostname);
+    if (hostent == NULL) {
+        fprintf(stderr, "error: gethostbyname(\"%s\")\n", hostname);
+        exit(EXIT_FAILURE);
+    }
+    in_addr = inet_addr(inet_ntoa(*(struct in_addr*)*(hostent->h_addr_list)));
+    if (in_addr == (in_addr_t)-1) {
+        fprintf(stderr, "error: inet_addr(\"%s\")\n", *(hostent->h_addr_list));
+        exit(EXIT_FAILURE);
+    }
+    sockaddr_in.sin_addr.s_addr = in_addr;
+    sockaddr_in.sin_family = AF_INET;
+    sockaddr_in.sin_port = htons(server_port);
+
+    /* Actually connect. */
+    if (connect(socket_file_descriptor, (struct sockaddr*)&sockaddr_in, sizeof(sockaddr_in)) == -1) {
+        perror("connect");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Send HTTP request. */
+    nbytes_total = 0;
+    while (nbytes_total < request_len) {
+        nbytes_last = write(socket_file_descriptor, request + nbytes_total, request_len - nbytes_total);
+        if (nbytes_last == -1) {
+            perror("write");
+            exit(EXIT_FAILURE);
+        }
+        nbytes_total += nbytes_last;
+    }
+
+    /* Read the response. */
+    fprintf(stderr, "debug: before first read\n");
+    while ((nbytes_total = read(socket_file_descriptor, buffer, BUFSIZ)) > 0) {
+        fprintf(stderr, "debug: after a read\n");
+        write(STDOUT_FILENO, buffer, nbytes_total);
+    }
+    fprintf(stderr, "debug: after last read\n");
+    if (nbytes_total == -1) {
+        perror("read");
+        exit(EXIT_FAILURE);
+    }
+
+    close(socket_file_descriptor);
+    exit(EXIT_SUCCESS);
+}