Rearrange and tidy up code in guestfsd.c

This just tidies up the main() function in the daemon.  There is
no longer a huge fixed-sized buffer used for the kernel command
line.  Variables are moved closer to where they are used.  Some
local variables turned out to be unused - these are removed.  Finally
the part that reads the kernel command line is moved into a separate
function.

There is only minimal functional change here (it now prints out
the kernel command line).

Literal '4' replaced with 'sizeof' expression, at Jim Meyering's
suggestion during patch review.

diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
index bfd8139..b4fb15e 100644 (file)
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -41,10 +41,11 @@
 #include "daemon.h"
 
 static void usage (void);
+static char *read_cmdline (void);
 
 /* Also in guestfs.c */
-#define GUESTFWD_PORT "6666"
 #define GUESTFWD_ADDR "10.0.2.4"
+#define GUESTFWD_PORT "6666"
 
 int verbose = 0;
 
@@ -73,17 +74,9 @@ main (int argc, char *argv[])
     { "help", 0, 0, '?' },
     { 0, 0, 0, 0 }
   };
-  int c, n, r;
+  int c;
   int dont_fork = 0;
-  FILE *fp;
-  char buf[4096];
-  char *p, *p2;
-  int sock;
-  struct addrinfo *res, *rr;
-  struct addrinfo hints;
-  XDR xdr;
-  uint32_t len;
-  struct sigaction sa;
+  char *cmdline;
 
 #ifdef HAVE_REGISTER_PRINTF_SPECIFIER
   /* http://udrepper.livejournal.com/20948.html */
@@ -122,22 +115,22 @@ main (int argc, char *argv[])
     exit (1);
   }
 
-  /* Set the verbose flag. */
-  fp = fopen ("/proc/cmdline", "r");
-  if (fp == NULL) {
-    perror ("/proc/cmdline");
-    goto next;
-  }
-  n = fread (buf, 1, sizeof buf - 1, fp);
-  fclose (fp);
-  buf[n] = '\0';
+  cmdline = read_cmdline ();
 
-  verbose = strstr (buf, "guestfs_verbose=1") != NULL;
+  /* Set the verbose flag. */
+  verbose = cmdline && strstr (cmdline, "guestfs_verbose=1") != NULL;
   if (verbose)
     printf ("verbose daemon enabled\n");
 
- next:
+  if (verbose) {
+    if (cmdline)
+      printf ("linux commmand line: %s\n", cmdline);
+    else
+      printf ("could not read linux command line\n");
+  }
+
   /* Make sure SIGPIPE doesn't kill us. */
+  struct sigaction sa;
   memset (&sa, 0, sizeof sa);
   sa.sa_handler = SIG_IGN;
   sa.sa_flags = 0;
@@ -156,6 +149,9 @@ main (int argc, char *argv[])
   umask (022);
 
   /* Resolve the hostname. */
+  struct addrinfo *res, *rr;
+  struct addrinfo hints;
+  int r;
   memset (&hints, 0, sizeof hints);
   hints.ai_socktype = SOCK_STREAM;
   hints.ai_flags = AI_ADDRCONFIG;
@@ -167,7 +163,7 @@ main (int argc, char *argv[])
   }
 
   /* Connect to the given TCP socket. */
-  sock = -1;
+  int sock = -1;
   for (rr = res; rr != NULL; rr = rr->ai_next) {
     sock = socket (rr->ai_family, rr->ai_socktype, rr->ai_protocol);
     if (sock != -1) {
@@ -190,14 +186,13 @@ main (int argc, char *argv[])
   /* Send the magic length message which indicates that
    * userspace is up inside the guest.
    */
-  len = GUESTFS_LAUNCH_FLAG;
-  xdrmem_create (&xdr, buf, sizeof buf, XDR_ENCODE);
-  if (!xdr_uint32_t (&xdr, &len)) {
-    fprintf (stderr, "xdr_uint32_t failed\n");
-    exit (1);
-  }
+  char lenbuf[4];
+  XDR xdr;
+  uint32_t len = GUESTFS_LAUNCH_FLAG;
+  xdrmem_create (&xdr, lenbuf, sizeof lenbuf, XDR_ENCODE);
+  xdr_uint32_t (&xdr, &len);
 
-  if (xwrite (sock, buf, xdr_getpos (&xdr)) == -1)
+  if (xwrite (sock, lenbuf, sizeof lenbuf) == -1)
     exit (1);
 
   xdr_destroy (&xdr);
@@ -216,6 +211,55 @@ main (int argc, char *argv[])
   exit (0);
 }
 
+/* Read /proc/cmdline. */
+static char *
+read_cmdline (void)
+{
+  int fd = open ("/proc/cmdline", O_RDONLY);
+  if (fd == -1) {
+    perror ("/proc/cmdline");
+    return NULL;
+  }
+
+  size_t len = 0;
+  ssize_t n;
+  char buf[256];
+  char *r = NULL;
+
+  for (;;) {
+    n = read (fd, buf, sizeof buf);
+    if (n == -1) {
+      perror ("read");
+      free (r);
+      close (fd);
+      return NULL;
+    }
+    if (n == 0)
+      break;
+    char *newr = realloc (r, len + n + 1); /* + 1 is for terminating NUL */
+    if (newr == NULL) {
+      perror ("realloc");
+      free (r);
+      close (fd);
+      return NULL;
+    }
+    r = newr;
+    memcpy (&r[len], buf, n);
+    len += n;
+  }
+
+  if (r)
+    r[len] = '\0';
+
+  if (close (fd) == -1) {
+    perror ("close");
+    free (r);
+    return NULL;
+  }
+
+  return r;
+}
+
 /* Turn "/path" into "/sysroot/path".
  *
  * Caller must check for NULL and call reply_with_perror ("malloc")