[Qemu-devel] [PATCH v7 2/5] sockets: Change inet_parse() to accept address specification without port

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

sockets: Change inet_parse() to accept address specification without port

From: Bharata B Rao <bharata@linux.vnet.ibm.com>

inet_parse() expects address:port. Change it to work without explicit port
specification. In addition, don't depend solely on the return value of
sscanf but also consider the value obtained for %n directive used in sscanf.
This ensures that the scanning of malformed inet address isn't flagged as
success.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---

 qemu-sockets.c |   32 +++++++++++++++++++++++++-------
 1 files changed, 25 insertions(+), 7 deletions(-)


diff --git a/qemu-sockets.c b/qemu-sockets.c
index c330fc5..627269f 100644
--- a/qemu-sockets.c
+++ b/qemu-sockets.c
@@ -376,26 +376,35 @@ err:
     return -1;
 }
 
-/* compatibility wrapper */
+/*
+ * sscanf could return positive return value indicating successful
+ * match and assignment even when it doesn't parse the input as per
+ * the format specified. Hence we are depending on %n to really determine if
+ * inputs were successfully scanned. Checking retval for EOF isn't strictly
+ * necessary, but just being extra careful.
+ */
 int inet_parse(QemuOpts *opts, const char *str)
 {
     const char *optstr, *h;
     char addr[64];
-    char port[33];
-    int pos;
+    char port[33] = {'\0'}; /* port is optional */
+    int ret, pos, addr_pos = -1, port_pos = -1;
 
     /* parse address */
     if (str[0] == ':') {
         /* no host given */
         addr[0] = '\0';
-        if (1 != sscanf(str,":%32[^,]%n",port,&pos)) {
+        ret = sscanf(str, ":%32[^,]%n", port, &port_pos);
+        if (port_pos == -1 || ret == EOF) {
             fprintf(stderr, "%s: portonly parse error (%s)\n",
                     __FUNCTION__, str);
             return -1;
         }
     } else if (str[0] == '[') {
         /* IPv6 addr */
-        if (2 != sscanf(str,"[%64[^]]]:%32[^,]%n",addr,port,&pos)) {
+        ret = sscanf(str, "[%64[^]]]%n:%32[^,]%n", addr, &addr_pos,
+            port, &port_pos);
+        if (addr_pos == -1 || ret == EOF) {
             fprintf(stderr, "%s: ipv6 parse error (%s)\n",
                     __FUNCTION__, str);
             return -1;
@@ -403,7 +412,9 @@ int inet_parse(QemuOpts *opts, const char *str)
         qemu_opt_set(opts, "ipv6", "on");
     } else if (qemu_isdigit(str[0])) {
         /* IPv4 addr */
-        if (2 != sscanf(str,"%64[0-9.]:%32[^,]%n",addr,port,&pos)) {
+        ret = sscanf(str, "%64[0-9.]%n:%32[^,]%n", addr, &addr_pos,
+            port, &port_pos);
+        if (addr_pos == -1 || ret == EOF) {
             fprintf(stderr, "%s: ipv4 parse error (%s)\n",
                     __FUNCTION__, str);
             return -1;
@@ -411,7 +422,9 @@ int inet_parse(QemuOpts *opts, const char *str)
         qemu_opt_set(opts, "ipv4", "on");
     } else {
         /* hostname */
-        if (2 != sscanf(str,"%64[^:]:%32[^,]%n",addr,port,&pos)) {
+        ret = sscanf(str, "%64[^:]%n:%32[^,]%n", addr, &addr_pos,
+            port, &port_pos);
+        if (addr_pos == -1 || ret == EOF) {
             fprintf(stderr, "%s: hostname parse error (%s)\n",
                     __FUNCTION__, str);
             return -1;
@@ -421,6 +434,11 @@ int inet_parse(QemuOpts *opts, const char *str)
     qemu_opt_set(opts, "port", port);
 
     /* parse options */
+    if (port_pos != -1) {
+        pos = port_pos;
+    } else {
+        pos = addr_pos;
+    }
     optstr = str + pos;
     h = strstr(optstr, ",to=");
     if (h)