Libguestfs - Sep 2009 - [PATCH] Remove explicit guestfs=10.0.2.4:6666 kernel command line parameter.

This patch is in preparation for allowing libguestfs to use alternate
"vmchannel" implementations.

Although it's not a functional change, I think it is worthwhile on its
own because use of the term "vmchannel" in the names of constants is
inappropriate since (a) the "-net channel" option is now properly
known upstream as "guestfwd", and (b) no one can agree on what
"vmchannel" really means.

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
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>From 45630d4ac47511c5c0dc55a22fadba4b9236bf61 Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones at trick.home.annexia.org>
Date: Tue, 15 Sep 2009 17:14:44 +0100
Subject: [PATCH 4/5] Remove explicit guestfs=10.0.2.4:6666 kernel command line
parameter.

Since we control the appliance tightly, we can just specify
that it will always use a particular host and port, and we
don't need to pass it on the command line each time.

Also the VMCHANNEL_* constants are only relevant to the
particular guestfwd vmchannel implementation, so we rename
them as GUESTFWD_*.
---
 daemon/guestfsd.c |   78 ++++++++++++++--------------------------------------
 src/guestfs.c     |   10 +++----
 2 files changed, 25 insertions(+), 63 deletions(-)

diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
index af554bf..ebaf960 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -43,8 +43,8 @@
 static void usage (void);
 
 /* Also in guestfs.c */
-#define VMCHANNEL_PORT "6666"
-#define VMCHANNEL_ADDR "10.0.2.4"
+#define GUESTFWD_PORT "6666"
+#define GUESTFWD_ADDR "10.0.2.4"
 
 int verbose = 0;
 
@@ -67,18 +67,14 @@ int sysroot_len = 8;
 int
 main (int argc, char *argv[])
 {
-  static const char *options = "fh:p:?";
+  static const char *options = "f?";
   static const struct option long_options[] = {
     { "foreground", 0, 0, 'f' },
     { "help", 0, 0, '?' },
-    { "host", 1, 0, 'h' },
-    { "port", 1, 0, 'p' },
     { 0, 0, 0, 0 }
   };
   int c, n, r;
   int dont_fork = 0;
-  const char *host = NULL;
-  const char *port = NULL;
   FILE *fp;
   char buf[4096];
   char *p, *p2;
@@ -111,14 +107,6 @@ main (int argc, char *argv[])
       dont_fork = 1;
       break;
 
-    case 'h':
-      host = optarg;
-      break;
-
-    case 'p':
-      port = optarg;
-      break;
-
     case '?':
       usage ();
       exit (0);
@@ -134,47 +122,21 @@ main (int argc, char *argv[])
     exit (1);
   }
 
-  /* If host and port aren't set yet, try /proc/cmdline. */
-  if (!host || !port) {
-    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';
-
-    /* Set the verbose flag.  Not quite right because this will only
-     * set the flag if host and port aren't set on the command line.
-     * Don't worry about this for now. (XXX)
-     */
-    verbose = strstr (buf, "guestfs_verbose=1") != NULL;
-    if (verbose)
-      printf ("verbose daemon enabled\n");
-
-    p = strstr (buf, "guestfs=");
-
-    if (p) {
-      p += 8;
-      p2 = strchr (p, ':');
-      if (p2) {
-        *p2++ = '\0';
-        host = p;
-        r = strcspn (p2, " \n");
-        p2[r] = '\0';
-        port = p2;
-      }
-    }
+  /* 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';
 
- next:
-  /* Can't parse /proc/cmdline, so use built-in defaults. */
-  if (!host || !port) {
-    host = VMCHANNEL_ADDR;
-    port = VMCHANNEL_PORT;
-  }
+  verbose = strstr (buf, "guestfs_verbose=1") != NULL;
+  if (verbose)
+    printf ("verbose daemon enabled\n");
 
+ next:
   /* Make sure SIGPIPE doesn't kill us. */
   memset (&sa, 0, sizeof sa);
   sa.sa_handler = SIG_IGN;
@@ -197,9 +159,10 @@ main (int argc, char *argv[])
   memset (&hints, 0, sizeof hints);
   hints.ai_socktype = SOCK_STREAM;
   hints.ai_flags = AI_ADDRCONFIG;
-  r = getaddrinfo (host, port, &hints, &res);
+  r = getaddrinfo (GUESTFWD_ADDR, GUESTFWD_PORT, &hints, &res);
   if (r != 0) {
-    fprintf (stderr, "%s:%s: %s\n", host, port, gai_strerror (r));
+    fprintf (stderr, "%s:%s: %s\n",
+             GUESTFWD_ADDR, GUESTFWD_PORT, gai_strerror (r));
     exit (1);
   }
 
@@ -219,7 +182,8 @@ main (int argc, char *argv[])
   freeaddrinfo (res);
 
   if (sock == -1) {
-    fprintf (stderr, "connection to %s:%s failed\n", host, port);
+    fprintf (stderr, "connection to %s:%s failed\n",
+             GUESTFWD_ADDR, GUESTFWD_PORT);
     exit (1);
   }
 
@@ -317,7 +281,7 @@ xread (int sock, void *v_buf, size_t len)
 static void
 usage (void)
 {
-  fprintf (stderr, "guestfsd [-f] [-h host -p port]\n");
+  fprintf (stderr, "guestfsd [-f]\n");
 }
 
 int
diff --git a/src/guestfs.c b/src/guestfs.c
index e9961d1..0c97cea 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -85,8 +85,8 @@ static void close_handles (void);
 #define UNIX_PATH_MAX 108
 
 /* Also in guestfsd.c */
-#define VMCHANNEL_PORT 6666
-#define VMCHANNEL_ADDR "10.0.2.4"
+#define GUESTFWD_PORT 6666
+//#define GUESTFWD_ADDR "10.0.2.4"
 
 /* GuestFS handle and connection. */
 enum state { CONFIG, LAUNCHING, READY, BUSY, NO_HANDLE };
@@ -1003,11 +1003,9 @@ guestfs__launch (guestfs_h *g)
     /* Linux kernel command line. */
     snprintf (append, sizeof append,
               LINUX_CMDLINE
-              "guestfs=%s:%d "
               "%s"              /* (selinux) */
               "%s"              /* (verbose) */
               "%s",             /* (append) */
-              VMCHANNEL_ADDR, VMCHANNEL_PORT,
               g->selinux ? "selinux=1 enforcing=0 " :
"selinux=0 ",
               g->verbose ? "guestfs_verbose=1 " : " ",
               g->append ? g->append : "");
@@ -1038,7 +1036,7 @@ guestfs__launch (guestfs_h *g)
        */
       snprintf (vmchannel, sizeof vmchannel,
                
"user,vlan=0,net=10.0.2.0/8,guestfwd=tcp:%s:%d-unix:%s,server,nowait",
-                VMCHANNEL_ADDR, VMCHANNEL_PORT, unixsock);
+                GUESTFWD_ADDR, GUESTFWD_PORT, unixsock);
 
       add_cmdline (g, "-net");
       add_cmdline (g, vmchannel);
@@ -1049,7 +1047,7 @@ guestfs__launch (guestfs_h *g)
        */
       snprintf (vmchannel, sizeof vmchannel,
                 "channel,%d:unix:%s,server,nowait",
-                VMCHANNEL_PORT, unixsock);
+                GUESTFWD_PORT, unixsock);
 
       add_cmdline (g, "-net");
       add_cmdline (g, vmchannel);
-- 
1.6.2.5

Richard W.M. Jones wrote:
> This patch is in preparation for allowing libguestfs to use alternate
> "vmchannel" implementations.
>
> Although it's not a functional change, I think it is worthwhile on its
> own because use of the term "vmchannel" in the names of constants
is
> inappropriate since (a) the "-net channel" option is now properly
> known upstream as "guestfwd", and (b) no one can agree on what
> "vmchannel" really means.
...
>>From 45630d4ac47511c5c0dc55a22fadba4b9236bf61 Mon Sep 17 00:00:00 2001
> From: Richard Jones <rjones at trick.home.annexia.org>
> Date: Tue, 15 Sep 2009 17:14:44 +0100
> Subject: [PATCH 4/5] Remove explicit guestfs=10.0.2.4:6666 kernel command
line parameter.
>
> Since we control the appliance tightly, we can just specify
> that it will always use a particular host and port, and we
> don't need to pass it on the command line each time.
>
> Also the VMCHANNEL_* constants are only relevant to the
> particular guestfwd vmchannel implementation, so we rename
> them as GUESTFWD_*.
> ---
>  daemon/guestfsd.c |   78
++++++++++++++--------------------------------------
>  src/guestfs.c     |   10 +++----
>  2 files changed, 25 insertions(+), 63 deletions(-)
>
> diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
> index af554bf..ebaf960 100644
> --- a/daemon/guestfsd.c
> +++ b/daemon/guestfsd.c
> @@ -43,8 +43,8 @@
>  static void usage (void);
>
>  /* Also in guestfs.c */
> -#define VMCHANNEL_PORT "6666"
> -#define VMCHANNEL_ADDR "10.0.2.4"
> +#define GUESTFWD_PORT "6666"
> +#define GUESTFWD_ADDR "10.0.2.4"
All looks good, though this seems like it *is* a functional
change, since it removes the -h and -p options below.

Two questions:

First, note the definition of GUESTFWD_ADDR above
Why the commented-out one below (in src/guestfs.c):

  //#define GUESTFWD_ADDR "10.0.2.4"


Second, I saw this in the context:
>    /* Make sure SIGPIPE doesn't kill us. */
>    memset (&sa, 0, sizeof sa);
>    sa.sa_handler = SIG_IGN;
Have you considered alternate ways of ignoring SIGPIPE?
Ignoringn SIGPIPE across the board can cause problems (albeit subtle)
in unsuspecting child processes.