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

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=84fc40f6b2dea9e0b455675ea9123d03699830ef

commit 84fc40f6b2dea9e0b455675ea9123d03699830ef
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Mon Feb 28 19:00:23 2022 +0530

    gaih_inet: Simplify canon name resolution
    
    Simplify logic for allocation of canon to remove the canonbuf variable;
    canon now always points to an allocated block.  Also pull the canon name
    set into a separate function.
    
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 sysdeps/posix/getaddrinfo.c | 109 +++++++++++++++++++++++---------------------
 1 file changed, 56 insertions(+), 53 deletions(-)

diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 43a8c7e266..ea3fa76748 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -336,7 +336,7 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req,
 	pat = &((*pat)->next);						      \
       if (localcanon != NULL && canon == NULL)				      \
 	{								      \
-	  canonbuf = __strdup (localcanon);				      \
+	  char *canonbuf = __strdup (localcanon);			      \
 	  if (canonbuf == NULL)						      \
 	    {								      \
 	      __resolv_context_put (res_ctx);				      \
@@ -768,6 +768,38 @@ simple_gethostbyname (const char *name, const struct addrinfo *req,
   return -EAI_NODATA;
 }
 
+static int
+process_canonname (const struct addrinfo *req, const char *orig_name,
+		   char **canonp)
+{
+  char *canon = *canonp;
+
+  if ((req->ai_flags & AI_CANONNAME) != 0)
+    {
+      bool do_idn = req->ai_flags & AI_CANONIDN;
+      if (do_idn)
+	{
+	  char *out;
+	  int rc = __idna_from_dns_encoding (canon ?: orig_name, &out);
+	  if (rc == 0)
+	    {
+	      free (canon);
+	      canon = out;
+	    }
+	  else if (rc == EAI_IDN_ENCODE)
+	    /* Use the punycode name as a fallback.  */
+	    do_idn = false;
+	  else
+	    return -rc;
+	}
+      if (!do_idn && canon == NULL && (canon = __strdup (orig_name)) == NULL)
+	return -EAI_MEMORY;
+    }
+
+  *canonp = canon;
+  return 0;
+}
+
 static int
 gaih_inet (const char *name, const struct gaih_service *service,
 	   const struct addrinfo *req, struct addrinfo **pai,
@@ -778,7 +810,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 
   struct gaih_addrtuple *at = NULL;
   bool got_ipv6 = false;
-  const char *canon = NULL;
+  char *canon = NULL;
   const char *orig_name = name;
 
   /* Reserve stack memory for the scratch buffer in the getaddrinfo
@@ -790,7 +822,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
     return rc;
 
   bool malloc_name = false;
-  char *canonbuf = NULL;
   int result = 0;
   struct gaih_lookup_result res = {0};
   struct scratch_buffer resbuf;
@@ -815,7 +846,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
       else if (res.at != NULL)
 	{
 	  at = res.at;
-	  canon = canonbuf = at->name;
+	  canon = at->name;
 	  goto process_list;
 	}
 
@@ -839,12 +870,14 @@ gaih_inet (const char *name, const struct gaih_service *service,
       else if (res.at != NULL)
 	{
 	  at = res.at;
-	  canon = canonbuf = at->name;
+	  canon = at->name;
 	  got_ipv6 = res.got_ipv6;
 	  goto process_list;
 	}
 #endif
 
+      /* For NSS lookups, use PAT to track the end of the tuple list so that
+	 multiple lookups append to the end of the latest list.  */
       struct gaih_addrtuple **pat = &at;
       int no_data = 0;
       int no_inet6_data = 0;
@@ -920,7 +953,16 @@ gaih_inet (const char *name, const struct gaih_service *service,
 		  no_data = 1;
 
 		  if ((req->ai_flags & AI_CANONNAME) != 0 && canon == NULL)
-		    canon = (*pat)->name;
+		    {
+		      char *canonbuf = __strdup ((*pat)->name);
+		      if (canonbuf == NULL)
+			{
+			  __resolv_context_put (res_ctx);
+			  result = -EAI_MEMORY;
+			  goto free_and_return;
+			}
+		      canon = canonbuf;
+		    }
 
 		  while (*pat != NULL)
 		    {
@@ -1004,7 +1046,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
 		      if ((req->ai_flags & AI_CANONNAME) != 0
 			  && canon == NULL)
 			{
-			  canonbuf = getcanonname (nip, at, name);
+			  char *canonbuf = getcanonname (nip, at, name);
 			  if (canonbuf == NULL)
 			    {
 			      __resolv_context_put (res_ctx);
@@ -1052,8 +1094,8 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	    {
 	      at = NULL;
 	      pat = &at;
-	      free (canonbuf);
-	      canon = canonbuf = NULL;
+	      free (canon);
+	      canon = NULL;
 	    }
 
 	  nip++;
@@ -1121,6 +1163,10 @@ gaih_inet (const char *name, const struct gaih_service *service,
     }
 
   {
+    /* Set up the canonical name if we need it.  */
+    if ((result = process_canonname (req, orig_name, &canon)) != 0)
+      goto free_and_return;
+
     struct gaih_addrtuple *at2 = at;
     size_t socklen;
     sa_family_t family;
@@ -1130,48 +1176,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
      */
     while (at2 != NULL)
       {
-	/* Only the first entry gets the canonical name.  */
-	if (at2 == at && (req->ai_flags & AI_CANONNAME) != 0)
-	  {
-	    if (canon == NULL)
-	      /* If the canonical name cannot be determined, use
-		 the passed in string.  */
-	      canon = orig_name;
-
-	    bool do_idn = req->ai_flags & AI_CANONIDN;
-	    if (do_idn)
-	      {
-		char *out;
-		int rc = __idna_from_dns_encoding (canon, &out);
-		if (rc == 0)
-		  canon = out;
-		else if (rc == EAI_IDN_ENCODE)
-		  /* Use the punycode name as a fallback.  */
-		  do_idn = false;
-		else
-		  {
-		    result = -rc;
-		    goto free_and_return;
-		  }
-	      }
-	    if (!do_idn)
-	      {
-		if (canonbuf != NULL)
-		  /* We already allocated the string using malloc, but
-		     the buffer is now owned by canon.  */
-		  canonbuf = NULL;
-		else
-		  {
-		    canon = __strdup (canon);
-		    if (canon == NULL)
-		      {
-			result = -EAI_MEMORY;
-			goto free_and_return;
-		      }
-		  }
-	      }
-	  }
-
 	family = at2->family;
 	if (family == AF_INET6)
 	  {
@@ -1194,7 +1198,6 @@ gaih_inet (const char *name, const struct gaih_service *service,
 	    ai = *pai = malloc (sizeof (struct addrinfo) + socklen);
 	    if (ai == NULL)
 	      {
-		free ((char *) canon);
 		result = -EAI_MEMORY;
 		goto free_and_return;
 	      }
@@ -1253,7 +1256,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
  free_and_return:
   if (malloc_name)
     free ((char *) name);
-  free (canonbuf);
+  free (canon);
   gaih_lookup_result_free (&res);
   scratch_buffer_free (&resbuf);