Revert API change - maintain 9.x compatibility. (apache#478)

example/plugins/c-api/protocol/TxnSM.c

@@ -477,8 +477,6 @@ int
 state_dns_lookup(TSCont contp, TSEvent event, TSHostLookupResult host_info)
 {
   TxnSM *txn_sm = (TxnSM *)TSContDataGet(contp);
-  struct sockaddr_storage q_server_addr;
-  struct sockaddr_in *addr;
 
   TSDebug(PLUGIN_NAME, "enter state_dns_lookup");
 
@@ -489,16 +487,16 @@ state_dns_lookup(TSCont contp, TSEvent event, TSHostLookupResult host_info)
   txn_sm->q_pending_action = NULL;
 
   /* Get the server IP from data structure TSHostLookupResult. */
-  TSHostLookupResultAddrGet(host_info, (struct sockaddr *)&q_server_addr);
+  struct sockaddr const *sa = TSHostLookupResultAddrGet(host_info);
 
   /* Connect to the server using its IP. */
   set_handler(txn_sm->q_current_handler, (TxnSMHandler)&state_connect_to_server);
   TSAssert(txn_sm->q_pending_action == NULL);
-  TSAssert(q_server_addr.ss_family == AF_INET); /* NO IPv6 in this plugin */
-  addr = (struct sockaddr_in *)(&q_server_addr);
+  TSAssert(sa->sa_family == AF_INET); /* NO IPv6 in this plugin */
+  struct sockaddr_in *addr = (struct sockaddr_in *)(sa);
 
   addr->sin_port           = txn_sm->q_server_port;
-  txn_sm->q_pending_action = TSNetConnect(contp, (struct sockaddr const *)addr);
+  txn_sm->q_pending_action = TSNetConnect(contp, sa);
 
   return TS_SUCCESS;
 }

include/ts/ts.h

@@ -1929,10 +1929,9 @@ tsapi TSAction TSHostLookup(TSCont contp, const char *hostname, size_t namelen);
 /** Retrieve an address from the host lookup.
  *
  * @param lookup_result Result handle passed to event callback.
- * @param dst Destination for copying the address.
- * @return @c TS_SUCCESS if the address was available and copied, @c TS_ERROR otherwise.
+ * @return A @c sockaddr with the address if successful, a @c nullptr if not.
  */
-tsapi TSReturnCode TSHostLookupResultAddrGet(TSHostLookupResult lookup_result, struct sockaddr *dst);
+tsapi struct sockaddr const *TSHostLookupResultAddrGet(TSHostLookupResult lookup_result);
 
 /* TODO: Eventually, we might want something like this as well, but it requires
    support for building the HostDBInfo struct:

plugins/lua/ts_lua_misc.c

@@ -476,13 +476,14 @@ ts_lua_host_lookup_handler(TSCont contp, TSEvent event, void *edata)
   } else if (!edata) {
     lua_pushnil(L);
   } else {
-    struct sockaddr_storage addr;
-    TSHostLookupResult record = (TSHostLookupResult)edata;
-    TSHostLookupResultAddrGet(record, (struct sockaddr *)&addr);
-    if (addr.ss_family == AF_INET) {
-      inet_ntop(AF_INET, (const void *)&((struct sockaddr_in *)&addr)->sin_addr, cip, sizeof(cip));
+    TSHostLookupResult record   = (TSHostLookupResult)edata;
+    struct sockaddr const *addr = TSHostLookupResultAddrGet(record);
+    if (addr->sa_family == AF_INET) {
+      inet_ntop(AF_INET, &((struct sockaddr_in const *)&addr)->sin_addr, cip, sizeof(cip));
+    } else if (addr->sa_family == AF_INET6) {
+      inet_ntop(AF_INET6, &((struct sockaddr_in6 const *)&addr)->sin6_addr, cip, sizeof(cip));
     } else {
-      inet_ntop(AF_INET6, (const void *)&((struct sockaddr_in6 *)&addr)->sin6_addr, cip, sizeof(cip));
+      cip[0] = 0;
     }
     lua_pushstring(L, cip);
   }

src/traffic_server/InkAPI.cc

@@ -7436,6 +7436,30 @@ TSNetAcceptNamedProtocol(TSCont contp, const char *protocol)
 }
 
 /* DNS Lookups */
+/// Context structure for the lookup callback to the plugin.
+struct TSResolveInfo {
+  IpEndpoint addr;                ///< Lookup result.
+  HostDBRecord *record = nullptr; ///< Record for the FQDN.
+};
+
+int
+TSHostLookupTrampoline(TSCont contp, TSEvent ev, void *data)
+{
+  auto c = reinterpret_cast<INKContInternal *>(contp);
+  // Set up the local context.
+  TSResolveInfo ri;
+  ri.record = static_cast<HostDBRecord *>(data);
+  if (ri.record) {
+    ri.record->rr_info()[0].data.ip.toSockAddr(ri.addr);
+  }
+  auto *target = reinterpret_cast<INKContInternal *>(c->mdata);
+  // Deliver the message.
+  target->handleEvent(ev, &ri);
+  // Cleanup.
+  c->destroy();
+  return TS_SUCCESS;
+};
+
 TSAction
 TSHostLookup(TSCont contp, const char *hostname, size_t namelen)
 {
@@ -7445,22 +7469,23 @@ TSHostLookup(TSCont contp, const char *hostname, size_t namelen)
 
   FORCE_PLUGIN_SCOPED_MUTEX(contp);
 
-  INKContInternal *i = (INKContInternal *)contp;
-  return (TSAction)hostDBProcessor.getbyname_re(i, hostname, namelen);
+  // There is no place to store the actual sockaddr to which a pointer should be returned.
+  // therefore an intermediate continuation is created to intercept the reply from HostDB.
+  // Its handler can create the required sockaddr context on the stack and then forward
+  // the event to the plugin continuation. The sockaddr cannot be placed in the HostDB
+  // record because that is a shared object.
+  auto bouncer          = INKContAllocator.alloc();
+  bouncer->m_event_func = &TSHostLookupTrampoline;
+  bouncer->mdata        = contp;
+  return (TSAction)hostDBProcessor.getbyname_re(bouncer, hostname, namelen);
 }
 
-TSReturnCode
-TSHostLookupResultAddrGet(TSHostLookupResult lookup_result, sockaddr *dst)
+sockaddr const *
+TSHostLookupResultAddrGet(TSHostLookupResult lookup_result)
 {
   sdk_assert(sdk_sanity_check_hostlookup_structure(lookup_result) == TS_SUCCESS);
-  HostDBRecord::Handle record{reinterpret_cast<HostDBRecord *>(lookup_result)};
-  if (record) {
-    auto info = record->rr_info();
-    sdk_assert(info.size() > 0);
-    info[0].data.ip.toSockAddr(dst);
-    return TS_SUCCESS;
-  }
-  return TS_ERROR;
+  auto ri{reinterpret_cast<TSResolveInfo *>(lookup_result)};
+  return ri->addr.isValid() ? &ri->addr.sa : nullptr;
 }
 
 /*