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Re: [Qemu-devel] [PATCH 09/19] sockets: Chardev open error reporting, so

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH 09/19] sockets: Chardev open error reporting, sockets part
Date: Tue, 07 Feb 2012 09:13:10 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15 
On 02/07/2012 08:09 AM, Markus Armbruster wrote:

Convert to error_report().  This adds error locations to the messages,
which is particularly important when the location is buried in a
configuration file.  Moreover, we'll need this when we create a
monitor command to add character devices, so its errors actually
appear in the monitor, not stderr.

Also clean up the messages, and get rid of some that look like errors,
but aren't.

Improves user-hostile messages like this one for "-chardev
socket,id=foo,host=blackfin,port=1,server"

     inet_listen_opts: bind(ipv4,192.168.2.9,1): Permission denied
     chardev: opening backend "socket" failed

to

     qemu-system-x86_64: -chardev socket,id=foo,host=blackfin,port=1,server: 
Can't bind port blackfin:1: Permission denied
     chardev: opening backend "socket" failed

and this one for "-chardev udp,id=foo,localport=1,port=1"

     inet_dgram_opts: bind(ipv4,0.0.0.0,1): OK
     inet_dgram_opts failed
     chardev: opening backend "udp" failed

to

     qemu-system-x86_64: -chardev udp,id=foo,localport=1,port=1: Can't bind 
port :1: Permission denied
     chardev: opening backend "udp" failed

You got to love the "OK" part.

The uninformative extra "opening backend failed" message will be
cleaned up shortly.

Signed-off-by: Markus Armbruster<address@hidden>
---
  qemu-char.c    |    1 -
  qemu-sockets.c |  154 +++++++++++++++++++++++++------------------------------
  2 files changed, 70 insertions(+), 85 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index bb9e3f5..d591f70 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2101,7 +2101,6 @@ static CharDriverState *qemu_chr_open_udp(QemuOpts *opts)

      fd = inet_dgram_opts(opts);
      if (fd<  0) {
-        fprintf(stderr, "inet_dgram_opts failed\n");
          goto return_err;
      }


Let's add an Error ** argument here.
It's easy to bridge errors to error_report (qerror_report_err) so it's conducive to incremental refactoring. Plus it starts getting us away from terminal errors and into proper erroro propagation. 


diff --git a/qemu-sockets.c b/qemu-sockets.c
index 6bcb8e3..67e0559 100644
--- a/qemu-sockets.c
+++ b/qemu-sockets.c
@@ -20,7 +20,8 @@
  #include<unistd.h>

  #include "qemu_socket.h"
-#include "qemu-common.h" /* for qemu_isdigit */
+#include "qemu-common.h"
+#include "qemu-error.h"

  #ifndef AI_ADDRCONFIG
  # define AI_ADDRCONFIG 0
@@ -107,7 +108,7 @@ int inet_listen_opts(QemuOpts *opts, int port_offset)
      char port[33];
      char uaddr[INET6_ADDRSTRLEN+1];
      char uport[33];
-    int slisten, rc, to, port_min, port_max, p;
+    int slisten, rc, to, port_min, port_max, p, sav_errno;

      memset(&ai,0, sizeof(ai));
      ai.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
@@ -116,7 +117,7 @@ int inet_listen_opts(QemuOpts *opts, int port_offset)

      if ((qemu_opt_get(opts, "host") == NULL) ||
          (qemu_opt_get(opts, "port") == NULL)) {
-        fprintf(stderr, "%s: host and/or port not specified\n", __FUNCTION__);
+        error_report("inet socket character device requires parameters host and 
port");
          return -1;
      }
      pstrcpy(port, sizeof(port), qemu_opt_get(opts, "port"));
@@ -133,8 +134,8 @@ int inet_listen_opts(QemuOpts *opts, int port_offset)
          snprintf(port, sizeof(port), "%d", atoi(port) + port_offset);
      rc = getaddrinfo(strlen(addr) ? addr : NULL, port,&ai,&res);
      if (rc != 0) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
+        error_report("Can't resolve %s:%s: %s",
+                     addr, port, gai_strerror(rc));
          return -1;
      }

@@ -145,9 +146,7 @@ int inet_listen_opts(QemuOpts *opts, int port_offset)
                        NI_NUMERICHOST | NI_NUMERICSERV);
          slisten = qemu_socket(e->ai_family, e->ai_socktype, e->ai_protocol);
          if (slisten<  0) {
-            fprintf(stderr,"%s: socket(%s): %s\n", __FUNCTION__,
-                    inet_strfamily(e->ai_family), strerror(errno));
-            continue;
+            continue;           /* try next address */
          }

          setsockopt(slisten,SOL_SOCKET,SO_REUSEADDR,(void*)&on,sizeof(on));
@@ -166,25 +165,33 @@ int inet_listen_opts(QemuOpts *opts, int port_offset)
              if (bind(slisten, e->ai_addr, e->ai_addrlen) == 0) {
                  goto listen;
              }
-            if (p == port_max) {
-                fprintf(stderr,"%s: bind(%s,%s,%d): %s\n", __FUNCTION__,
-                        inet_strfamily(e->ai_family), uaddr, inet_getport(e),
-                        strerror(errno));
-            }
          }
+
+        sav_errno = errno;
          closesocket(slisten);
+        errno = sav_errno;
+        /* try next address */
+    }
+
+    /* no address worked, errno is from last failed socket() or bind() */
+    if (to) {
+        error_report("Can't bind any port %s:%s..%d: %s",
+                     addr, port, to, strerror(errno));
+    } else {
+        error_report("Can't bind port %s:%s: %s",
+                     addr, port, strerror(errno));
      }
-    fprintf(stderr, "%s: FAILED\n", __FUNCTION__);
      freeaddrinfo(res);
      return -1;

  listen:
      if (listen(slisten,1) != 0) {
-        perror("listen");
+        error_report("Can't listen on %s:%d: %s", addr, p, strerror(errno));
          closesocket(slisten);
          freeaddrinfo(res);
          return -1;
      }
+
      snprintf(uport, sizeof(uport), "%d", inet_getport(e) - port_offset);
      qemu_opt_set(opts, "host", uaddr);
      qemu_opt_set(opts, "port", uport);
@@ -199,8 +206,6 @@ int inet_connect_opts(QemuOpts *opts)
      struct addrinfo ai,*res,*e;
      const char *addr;
      const char *port;
-    char uaddr[INET6_ADDRSTRLEN+1];
-    char uport[33];
      int sock,rc;

      memset(&ai,0, sizeof(ai));
@@ -211,7 +216,7 @@ int inet_connect_opts(QemuOpts *opts)
      addr = qemu_opt_get(opts, "host");
      port = qemu_opt_get(opts, "port");
      if (addr == NULL || port == NULL) {
-        fprintf(stderr, "inet_connect: host and/or port not specified\n");
+        error_report("inet socket character device requires parameters host and 
port");
          return -1;
      }

@@ -222,38 +227,29 @@ int inet_connect_opts(QemuOpts *opts)

      /* lookup */
      if (0 != (rc = getaddrinfo(addr, port,&ai,&res))) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
+        error_report("Can't resolve %s:%s: %s",
+                     addr, port, gai_strerror(rc));
        return -1;
      }

      for (e = res; e != NULL; e = e->ai_next) {
-        if (getnameinfo((struct sockaddr*)e->ai_addr,e->ai_addrlen,
-                            uaddr,INET6_ADDRSTRLEN,uport,32,
-                            NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
-            fprintf(stderr,"%s: getnameinfo: oops\n", __FUNCTION__);
-            continue;
-        }
          sock = qemu_socket(e->ai_family, e->ai_socktype, e->ai_protocol);
          if (sock<  0) {
-            fprintf(stderr,"%s: socket(%s): %s\n", __FUNCTION__,
-            inet_strfamily(e->ai_family), strerror(errno));
-            continue;
+            continue;           /* try next address */
          }
          setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,(void*)&on,sizeof(on));

          /* connect to peer */
          if (connect(sock,e->ai_addr,e->ai_addrlen)<  0) {
-            if (NULL == e->ai_next)
-                fprintf(stderr, "%s: connect(%s,%s,%s,%s): %s\n", __FUNCTION__,
-                        inet_strfamily(e->ai_family),
-                        e->ai_canonname, uaddr, uport, strerror(errno));
              closesocket(sock);
-            continue;
+            continue;           /* try next address */
          }
          freeaddrinfo(res);
          return sock;
      }
+
+    /* no address worked, errno is from last failed socket() or connect() */
+    error_report("Can't connect to %s:%s: %s", addr, port, strerror(errno));
      freeaddrinfo(res);
      return -1;
  }
@@ -261,12 +257,9 @@ int inet_connect_opts(QemuOpts *opts)
  int inet_dgram_opts(QemuOpts *opts)
  {
      struct addrinfo ai, *peer = NULL, *local = NULL;
-    const char *addr;
-    const char *port;
-    char uaddr[INET6_ADDRSTRLEN+1];
-    char uport[33];
+    const char *addr, *port;
+    const char *localaddr, *localport;
      int sock = -1, rc;
-
      /* lookup peer addr */
      memset(&ai,0, sizeof(ai));
      ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG;
@@ -279,7 +272,7 @@ int inet_dgram_opts(QemuOpts *opts)
          addr = "localhost";
      }
      if (port == NULL || strlen(port) == 0) {
-        fprintf(stderr, "inet_dgram: port not specified\n");
+        error_report("udp character device requires parameter port");
          return -1;
      }

@@ -289,8 +282,8 @@ int inet_dgram_opts(QemuOpts *opts)
          ai.ai_family = PF_INET6;

      if (0 != (rc = getaddrinfo(addr, port,&ai,&peer))) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
+        error_report("Can't resolve %s:%s: %s",
+                     addr, port, gai_strerror(rc));
        return -1;
      }

@@ -300,53 +293,40 @@ int inet_dgram_opts(QemuOpts *opts)
      ai.ai_family = peer->ai_family;
      ai.ai_socktype = SOCK_DGRAM;

-    addr = qemu_opt_get(opts, "localaddr");
-    port = qemu_opt_get(opts, "localport");
-    if (addr == NULL || strlen(addr) == 0) {
-        addr = NULL;
+    localaddr = qemu_opt_get(opts, "localaddr");
+    localport = qemu_opt_get(opts, "localport");
+    if (localaddr == NULL || strlen(localaddr) == 0) {
+        localaddr = NULL;
      }
-    if (!port || strlen(port) == 0)
-        port = "0";
+    if (!localport || strlen(localport) == 0)
+        localport = "0";

-    if (0 != (rc = getaddrinfo(addr, port,&ai,&local))) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
+    if (0 != (rc = getaddrinfo(localaddr, localport,&ai,&local))) {
+        error_report("Can't resolve %s:%s: %s",
+                     localaddr ? localaddr : NULL, localport,
+                     gai_strerror(rc));
          return -1;
      }

      /* create socket */
      sock = qemu_socket(peer->ai_family, peer->ai_socktype, peer->ai_protocol);
      if (sock<  0) {
-        fprintf(stderr,"%s: socket(%s): %s\n", __FUNCTION__,
-                inet_strfamily(peer->ai_family), strerror(errno));
-        goto err;
+        goto cant_bind;
      }
      setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,(void*)&on,sizeof(on));

      /* bind socket */
-    if (getnameinfo((struct sockaddr*)local->ai_addr,local->ai_addrlen,
-                    uaddr,INET6_ADDRSTRLEN,uport,32,
-                    NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
-        fprintf(stderr, "%s: getnameinfo: oops\n", __FUNCTION__);
-        goto err;
-    }
      if (bind(sock, local->ai_addr, local->ai_addrlen)<  0) {
-        fprintf(stderr,"%s: bind(%s,%s,%d): OK\n", __FUNCTION__,
-                inet_strfamily(local->ai_family), uaddr, inet_getport(local));
+    cant_bind:
+        error_report("Can't bind port %s:%s: %s",
+                     localaddr ? localaddr : "", localport, strerror(errno));
          goto err;
      }

      /* connect to peer */
-    if (getnameinfo((struct sockaddr*)peer->ai_addr, peer->ai_addrlen,
-                    uaddr, INET6_ADDRSTRLEN, uport, 32,
-                    NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
-        fprintf(stderr, "%s: getnameinfo: oops\n", __FUNCTION__);
-        goto err;
-    }
      if (connect(sock,peer->ai_addr,peer->ai_addrlen)<  0) {
-        fprintf(stderr, "%s: connect(%s,%s,%s,%s): %s\n", __FUNCTION__,
-                inet_strfamily(peer->ai_family),
-                peer->ai_canonname, uaddr, uport, strerror(errno));
+        error_report("Can't connect to %s:%s: %s",
+                     addr, port, strerror(errno));
          goto err;
      }

@@ -471,8 +451,7 @@ int unix_listen_opts(QemuOpts *opts)

      sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
      if (sock<  0) {
-        perror("socket(unix)");
-        return -1;
+        goto err;
      }

      memset(&un, 0, sizeof(un));
@@ -496,18 +475,20 @@ int unix_listen_opts(QemuOpts *opts)

      unlink(un.sun_path);
      if (bind(sock, (struct sockaddr*)&un, sizeof(un))<  0) {
-        fprintf(stderr, "bind(unix:%s): %s\n", un.sun_path, strerror(errno));
          goto err;
      }
      if (listen(sock, 1)<  0) {
-        fprintf(stderr, "listen(unix:%s): %s\n", un.sun_path, strerror(errno));
          goto err;
      }

      return sock;

  err:
-    closesocket(sock);
+    error_report("Can't create socket %s: %s",
+                 un.sun_path, strerror(errno));
+    if (sock>= 0) {
+        closesocket(sock);
+    }
      return -1;
  }

@@ -518,26 +499,31 @@ int unix_connect_opts(QemuOpts *opts)
      int sock;

      if (NULL == path) {
-        fprintf(stderr, "unix connect: no path specified\n");
+        error_report("unix socket character device requires parameter path");
          return -1;
      }

      sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
      if (sock<  0) {
-        perror("socket(unix)");
-        return -1;
+        goto err;
      }

      memset(&un, 0, sizeof(un));
      un.sun_family = AF_UNIX;
      snprintf(un.sun_path, sizeof(un.sun_path), "%s", path);
      if (connect(sock, (struct sockaddr*)&un, sizeof(un))<  0) {
-        fprintf(stderr, "connect(unix:%s): %s\n", path, strerror(errno));
-        close(sock);
-       return -1;
+        goto err;
      }

      return sock;
+
+err:
+    error_report("Can't connect to socket %s: %s",
+                 un.sun_path, strerror(errno));
+    if (sock>= 0) {
+        close(sock);
+    }
+    return -1;
  }
Basically, same thing here and the remaining functions. Let's not introduce additional uses of error_report().
That said, I imagine you don't want to introduce a bunch of error types for these different things and that's probably not productive anyway.
So let's compromise and introduce a generic QERR_INTERNAL_ERROR that takes a single human readable string as an argument. We can have a wrapper for it that also records location information in the error object. 

Regards,

Anthony Liguori
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