[PATCH v5 3/5] inet_parse_host_and_addr: Recognize []:port (empty ipv6 address)

[Doug Evans via <qemu-devel@nongnu.org>]

Some callers need to distinguish empty ipv4 addresses from ipv6.

Signed-off-by: Doug Evans <dje@google.com>
---

Changes from v4:
- new in this patchset revision

 util/qemu-sockets.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index 3ca6a6fb3d..062f0eb074 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -620,7 +620,8 @@ static int inet_parse_flag(const char *flagname, const char *optstr, bool *val,
  * Terminator may be '\0'.
  * The syntax for IPv4 addresses is: address:port. "address" is optional,
  * and may be empty (i.e., str is ":port").
- * The syntax for IPv6 addresses is: [address]:port. Upon return the wrapping
+ * The syntax for IPv6 addresses is: [address]:port. "address" is optional,
+ * and may be empty (i.e., str is "[]:port"). Upon return the wrapping
  * [] brackets are removed.
  * Host names are also supported as hostname:port. It is up to the caller to
  * distinguish host names from numeric IPv4 addresses.
@@ -654,7 +655,10 @@ const char *inet_parse_host_and_port(const char *str, int terminator,
         }
     } else if (buf[0] == '[') {
         /* IPv6 addr */
-        if (sscanf(buf, "[%64[^]]]:%32s", host, port) != 2) {
+        /* Note: sscanf %[ doesn't recognize empty contents. */
+        if (sscanf(buf, "[]:%32s", port) == 1) {
+            host[0] = '\0';
+        } else if (sscanf(buf, "[%64[^]]]:%32s", host, port) != 2) {
             error_setg(errp, "error parsing IPv6 address '%s'", buf);
             return NULL;
         }
-- 
2.30.0.617.g56c4b15f3c-goog