[glibc/siddhesh/gai-cleanup2] gaih_inet: Simplify service resolution

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=cb85241ef95870d13010b52460952e3ea0d16a72

commit cb85241ef95870d13010b52460952e3ea0d16a72
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Thu Feb 10 13:27:11 2022 +0530

    gaih_inet: Simplify service resolution
    
    Refactor the code to split out the service resolution code into a
    separate function.  Allocate the service tuples array just once to the
    size of the typeproto array, thus avoiding the unnecessary pointer
    chasing and stack allocations.
    
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 sysdeps/posix/getaddrinfo.c | 178 +++++++++++++++++++-------------------------
 1 file changed, 78 insertions(+), 100 deletions(-)

diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 18dccd5924..3b6c106b0d 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -100,14 +100,12 @@ struct gaih_service
 
 struct gaih_servtuple
   {
-    struct gaih_servtuple *next;
     int socktype;
     int protocol;
     int port;
+    bool set;
   };
 
-static const struct gaih_servtuple nullserv;
-
 
 struct gaih_typeproto
   {
@@ -180,11 +178,11 @@ gaih_inet_serv (const char *servicename, const struct gaih_typeproto *tp,
     }
   while (r);
 
-  st->next = NULL;
   st->socktype = tp->socktype;
   st->protocol = ((tp->protoflag & GAI_PROTO_PROTOANY)
 		  ? req->ai_protocol : tp->protocol);
   st->port = s->s_port;
+  st->set = true;
 
   return 0;
 }
@@ -324,20 +322,11 @@ getcanonname (nss_action_list nip, struct gaih_addrtuple *at, const char *name)
 }
 
 static int
-gaih_inet (const char *name, const struct gaih_service *service,
-	   const struct addrinfo *req, struct addrinfo **pai,
-	   unsigned int *naddrs, struct scratch_buffer *tmpbuf)
+get_servtuples (const struct gaih_service *service, const struct addrinfo *req,
+		struct gaih_servtuple *st, struct scratch_buffer *tmpbuf)
 {
+  int i;
   const struct gaih_typeproto *tp = gaih_inet_typeproto;
-  struct gaih_servtuple *st = (struct gaih_servtuple *) &nullserv;
-  struct gaih_addrtuple *at = NULL;
-  bool got_ipv6 = false;
-  const char *canon = NULL;
-  const char *orig_name = name;
-
-  /* Reserve stack memory for the scratch buffer in the getaddrinfo
-     function.  */
-  size_t alloca_used = sizeof (struct scratch_buffer);
 
   if (req->ai_protocol || req->ai_socktype)
     {
@@ -359,98 +348,88 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	}
     }
 
-  int port = 0;
-  if (service != NULL)
+  if (service != NULL && (tp->protoflag & GAI_PROTO_NOSERVICE) != 0)
+    return -EAI_SERVICE;
+
+  if (service == NULL || service->num >= 0)
     {
-      if ((tp->protoflag & GAI_PROTO_NOSERVICE) != 0)
-	return -EAI_SERVICE;
+      int port = service != NULL ? htons (service->num) : 0;
 
-      if (service->num < 0)
+      if (req->ai_socktype || req->ai_protocol)
 	{
-	  if (tp->name[0])
-	    {
-	      st = (struct gaih_servtuple *)
-		alloca_account (sizeof (struct gaih_servtuple), alloca_used);
-
-	      int rc = gaih_inet_serv (service->name, tp, req, st, tmpbuf);
-	      if (__glibc_unlikely (rc != 0))
-		return rc;
-	    }
-	  else
-	    {
-	      struct gaih_servtuple **pst = &st;
-	      for (tp++; tp->name[0]; tp++)
-		{
-		  struct gaih_servtuple *newp;
+	  st[0].socktype = tp->socktype;
+	  st[0].protocol = ((tp->protoflag & GAI_PROTO_PROTOANY)
+			  ? req->ai_protocol : tp->protocol);
+	  st[0].port = port;
+	  st[0].set = true;
 
-		  if ((tp->protoflag & GAI_PROTO_NOSERVICE) != 0)
-		    continue;
+	  return 0;
+	}
 
-		  if (req->ai_socktype != 0
-		      && req->ai_socktype != tp->socktype)
-		    continue;
-		  if (req->ai_protocol != 0
-		      && !(tp->protoflag & GAI_PROTO_PROTOANY)
-		      && req->ai_protocol != tp->protocol)
-		    continue;
+      /* Neither socket type nor protocol is set.  Return all socket types
+	 we know about.  */
+      for (i = 0, ++tp; tp->name[0]; ++tp)
+	if (tp->defaultflag)
+	  {
+	    st[i].socktype = tp->socktype;
+	    st[i].protocol = tp->protocol;
+	    st[i].port = port;
+	    st[i++].set = true;
+	  }
 
-		  newp = (struct gaih_servtuple *)
-		    alloca_account (sizeof (struct gaih_servtuple),
-				    alloca_used);
+      return 0;
+    }
 
-		  if (gaih_inet_serv (service->name,
-				      tp, req, newp, tmpbuf) != 0)
-		    continue;
+  if (tp->name[0])
+    return gaih_inet_serv (service->name, tp, req, st, tmpbuf);
 
-		  *pst = newp;
-		  pst = &(newp->next);
-		}
-	      if (st == (struct gaih_servtuple *) &nullserv)
-		return -EAI_SERVICE;
-	    }
-	}
-      else
-	{
-	  port = htons (service->num);
-	  goto got_port;
-	}
-    }
-  else
+  for (i = 0, tp++; tp->name[0]; tp++)
     {
-    got_port:
+      if ((tp->protoflag & GAI_PROTO_NOSERVICE) != 0)
+	continue;
 
-      if (req->ai_socktype || req->ai_protocol)
-	{
-	  st = alloca_account (sizeof (struct gaih_servtuple), alloca_used);
-	  st->next = NULL;
-	  st->socktype = tp->socktype;
-	  st->protocol = ((tp->protoflag & GAI_PROTO_PROTOANY)
-			  ? req->ai_protocol : tp->protocol);
-	  st->port = port;
-	}
-      else
-	{
-	  /* Neither socket type nor protocol is set.  Return all socket types
-	     we know about.  */
-	  struct gaih_servtuple **lastp = &st;
-	  for (++tp; tp->name[0]; ++tp)
-	    if (tp->defaultflag)
-	      {
-		struct gaih_servtuple *newp;
+      if (req->ai_socktype != 0
+	  && req->ai_socktype != tp->socktype)
+	continue;
+      if (req->ai_protocol != 0
+	  && !(tp->protoflag & GAI_PROTO_PROTOANY)
+	  && req->ai_protocol != tp->protocol)
+	continue;
 
-		newp = alloca_account (sizeof (struct gaih_servtuple),
-				       alloca_used);
-		newp->next = NULL;
-		newp->socktype = tp->socktype;
-		newp->protocol = tp->protocol;
-		newp->port = port;
+      if (gaih_inet_serv (service->name,
+			  tp, req, &st[i], tmpbuf) != 0)
+	continue;
 
-		*lastp = newp;
-		lastp = &newp->next;
-	      }
-	}
+      i++;
     }
 
+  if (!st[0].set)
+    return -EAI_SERVICE;
+
+  return 0;
+}
+
+static int
+gaih_inet (const char *name, const struct gaih_service *service,
+	   const struct addrinfo *req, struct addrinfo **pai,
+	   unsigned int *naddrs, struct scratch_buffer *tmpbuf)
+{
+  struct gaih_servtuple st[sizeof (gaih_inet_typeproto)
+			   / sizeof (struct gaih_typeproto)] = {0};
+
+  struct gaih_addrtuple *at = NULL;
+  bool got_ipv6 = false;
+  const char *canon = NULL;
+  const char *orig_name = name;
+
+  /* Reserve stack memory for the scratch buffer in the getaddrinfo
+     function.  */
+  size_t alloca_used = sizeof (struct scratch_buffer);
+
+  int rc;
+  if ((rc = get_servtuples (service, req, st, tmpbuf)) != 0)
+    return rc;
+
   bool malloc_name = false;
   struct gaih_addrtuple *addrmem = NULL;
   char *canonbuf = NULL;
@@ -965,7 +944,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
     }
 
   {
-    struct gaih_servtuple *st2;
     struct gaih_addrtuple *at2 = at;
     size_t socklen;
     sa_family_t family;
@@ -1033,7 +1011,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	else
 	  socklen = sizeof (struct sockaddr_in);
 
-	for (st2 = st; st2 != NULL; st2 = st2->next)
+	for (int i = 0; st[i].set; i++)
 	  {
 	    struct addrinfo *ai;
 	    ai = *pai = malloc (sizeof (struct addrinfo) + socklen);
@@ -1046,8 +1024,8 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
 	    ai->ai_flags = req->ai_flags;
 	    ai->ai_family = family;
-	    ai->ai_socktype = st2->socktype;
-	    ai->ai_protocol = st2->protocol;
+	    ai->ai_socktype = st[i].socktype;
+	    ai->ai_protocol = st[i].protocol;
 	    ai->ai_addrlen = socklen;
 	    ai->ai_addr = (void *) (ai + 1);
 
@@ -1069,7 +1047,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 		struct sockaddr_in6 *sin6p =
 		  (struct sockaddr_in6 *) ai->ai_addr;
 
-		sin6p->sin6_port = st2->port;
+		sin6p->sin6_port = st[i].port;
 		sin6p->sin6_flowinfo = 0;
 		memcpy (&sin6p->sin6_addr,
 			at2->addr, sizeof (struct in6_addr));
@@ -1079,7 +1057,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	      {
 		struct sockaddr_in *sinp =
 		  (struct sockaddr_in *) ai->ai_addr;
-		sinp->sin_port = st2->port;
+		sinp->sin_port = st[i].port;
 		memcpy (&sinp->sin_addr,
 			at2->addr, sizeof (struct in_addr));
 		memset (sinp->sin_zero, '\0', sizeof (sinp->sin_zero));