getaddrinfo: implement canonname.

Paul A. Patience noted that the canonname_s variable is not
used in the C code. This indicates that the AI_CANONNAME
functionality of getaddrinfo isn't implemented. Let's do that.

* stdlib/socket.tl (sockaddr): New slot, canonname.
(addrinfo): Default canonname to nil, not 0, since it is
a string that may be absent.

* socket.c (getaddrinfo_wrap): If the first address object has
a non-null ai_canonname and it was requested via the flags,
then stick that name into every returned structure.

* txr.1: Documented.

3 files changed, 39 insertions, 5 deletions

diff --git a/socket.c b/socket.c
index c4745241..37158052 100644
--- a/socket.c
+++ b/socket.c
@@ -207,7 +207,9 @@ static val getaddrinfo_wrap(val node_in, val service_in, val hints_in)
   uw_catch_end;
 
   if (res == 0) {
+    val canonname = nil;
     for (aiter = alist; aiter; aiter = aiter->ai_next) {
+      val addr = nil;
       switch (aiter->ai_family) {
       case AF_INET:
         {
@@ -216,7 +218,7 @@ static val getaddrinfo_wrap(val node_in, val service_in, val hints_in)
             ipv4_addr_from_num(&sa->sin_addr, node);
           if (svc_num_p)
             sa->sin_port = htons(c_num(service, self));
-          ptail = list_collect(ptail, sockaddr_in_unpack(sa));
+          addr = sockaddr_in_unpack(sa);
         }
         break;
       case AF_INET6:
@@ -226,10 +228,18 @@ static val getaddrinfo_wrap(val node_in, val service_in, val hints_in)
             ipv6_addr_from_num(&sa->sin6_addr, node);
           if (svc_num_p)
             sa->sin6_port = ntohs(c_num(service, self));
-          ptail = list_collect(ptail, sockaddr_in6_unpack(sa));
+          addr = sockaddr_in6_unpack(sa);
         }
         break;
       }
+      if (addr) {
+        if (aiter == alist && (hints_ai.ai_flags & AI_CANONNAME) != 0
+            && aiter->ai_canonname)
+          canonname = string_utf8(aiter->ai_canonname);
+        if (canonname)
+          slotset(addr, canonname_s, canonname);
+        ptail = list_collect(ptail, addr);
+      }
     }
   }
 
diff --git a/stdlib/socket.tl b/stdlib/socket.tl
index 58f81e61..e07bea6b 100644
--- a/stdlib/socket.tl
+++ b/stdlib/socket.tl
@@ -25,6 +25,7 @@
 ;; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 (defstruct sockaddr nil
+  canonname ;; from getaddrinfo
   (:static family nil))
 
 (defstruct sockaddr-in sockaddr
@@ -46,7 +47,7 @@
   (family 0)
   (socktype 0)
   (protocol 0)
-  (canonname 0))
+  canonname)
 
 (defvarl shut-rd 0)
 (defvarl shut-wr 1)
diff --git a/txr.1 b/txr.1
index dfffc1b9..a45dae78 100644
--- a/txr.1
+++ b/txr.1
@@ -70174,6 +70174,7 @@ newly created datagram socket which is returned.
 .coNP Structure @ sockaddr
 .synb
 .mets (defstruct sockaddr nil
+.mets \ \  canonname
 .mets \ \  (:static family nil))
 .syne
 .desc
@@ -70186,11 +70187,22 @@ several other types are derived:
 and
 .codn sockaddr-un .
 
-It has a single slot called
+It has a single static slot named
 .code family
-which is static, and initialized to
+and a single instance slot
+.codn canonname ,
+both initialized to
 .codn nil .
 
+Note: the
+.code canonname
+slot is optionally by the
+.code getaddrinfo
+function on address structures that it returns, if requested via the
+.code ai-canonname
+flag. The slot only provides information to the application, playing no
+semantic role in addressing.
+
 .coNP Structure @ sockaddr-in
 .synb
 .mets (defstruct sockaddr-in sockaddr
@@ -70372,6 +70384,7 @@ flags: values given by the variables.
 .codn ai-passive ,
 .codn ai-numerichost ,
 .codn ai-v4mapped ,
+.codn ai-canonname ,
 .codn ai-all ,
 .code ai-addrconfig
 and
@@ -70381,6 +70394,16 @@ These correspond to the C constants
 .code AI_NUMERICHOST
 and so forth.
 
+If
+.code ai-canonname
+is specified, then every returned address structure will have its
+.code canonname
+member set to a string value rather than
+.codn nil .
+This string is a copy of the canonical name reported by the underlying
+C library function, which that function places only into the first
+returned address structure.
+
 The
 .code family
 slot holds an address family, which may be the value of