sockets/ud_ucase_sv.c

+/* ud_ucase_sv.c
+
+   A server that uses a UNIX domain datagram socket to receive datagrams,
+   convert their contents to uppercase, and then return them to the senders.
+
+   See also ud_ucase_cl.c.
+*/
 #include "ud_ucase.h"
 
 int
 main(int argc, char *argv[])
 {
     struct sockaddr_un svaddr, claddr;
     int sfd, j;
     ssize_t numBytes;
     socklen_t len;
     char buf[BUF_SIZE];
 
     sfd = socket(AF_UNIX, SOCK_DGRAM, 0);       /* Create server socket */
     if (sfd == -1)
         errExit("socket");
 
     /* Construct well-known address and bind server socket to it */
 
+    /* For an explanation of the following check, see the erratum note for
+       page 1168 at http://www.man7.org/tlpi/errata/. */
+
+    if (strlen(SV_SOCK_PATH) > sizeof(svaddr.sun_path) - 1)
+        fatal("Server socket path too long: %s", SV_SOCK_PATH);
+
     if (remove(SV_SOCK_PATH) == -1 && errno != ENOENT)
         errExit("remove-%s", SV_SOCK_PATH);
 
     memset(&svaddr, 0, sizeof(struct sockaddr_un));
     svaddr.sun_family = AF_UNIX;
     strncpy(svaddr.sun_path, SV_SOCK_PATH, sizeof(svaddr.sun_path) - 1);
 
     if (bind(sfd, (struct sockaddr *) &svaddr, sizeof(struct sockaddr_un)) == -1)
         errExit("bind");
 
     /* Receive messages, convert to uppercase, and return to client */
 
     for (;;) {
         len = sizeof(struct sockaddr_un);
         numBytes = recvfrom(sfd, buf, BUF_SIZE, 0,
                             (struct sockaddr *) &claddr, &len);
         if (numBytes == -1)
             errExit("recvfrom");
 
         printf("Server received %ld bytes from %s\n", (long) numBytes,
                 claddr.sun_path);
 
         for (j = 0; j < numBytes; j++)
             buf[j] = toupper((unsigned char) buf[j]);
 
         if (sendto(sfd, buf, numBytes, 0, (struct sockaddr *) &claddr, len) !=
                 numBytes)
             fatal("sendto");
     }
 }