migration/rdma: Fix rdma_getaddrinfo() error checking

rdma_getaddrinfo() returns 0 on success.  On error, it returns one of
the EAI_ error codes like getaddrinfo() does, or -1 with errno set.
This is broken by design: POSIX implicitly specifies the EAI_ error
codes to be non-zero, no more.  They could clash with -1.  Nothing we
can do about this design flaw.

Both callers of rdma_getaddrinfo() only recognize negative values as
error.  Works only because systems elect to make the EAI_ error codes
negative.

Best not to rely on that: change the callers to treat any non-zero
value as failure.  Also change them to return -1 instead of the value
received from getaddrinfo() on failure, to avoid positive error
values.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20230928132019.2544702-25-armbru@redhat.com>

migration/rdma.c

@@ -941,14 +941,14 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
 
     if (rdma->host == NULL || !strcmp(rdma->host, "")) {
         ERROR(errp, "RDMA hostname has not been set");
-        return -EINVAL;
+        return -1;
     }
 
     /* create CM channel */
     rdma->channel = rdma_create_event_channel();
     if (!rdma->channel) {
         ERROR(errp, "could not create CM channel");
-        return -EINVAL;
+        return -1;
     }
 
     /* create CM id */
@@ -962,7 +962,7 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
     port_str[15] = '\0';
 
     ret = rdma_getaddrinfo(rdma->host, port_str, NULL, &res);
-    if (ret < 0) {
+    if (ret) {
         ERROR(errp, "could not rdma_getaddrinfo address %s", rdma->host);
         goto err_resolve_get_addr;
     }
@@ -1004,7 +1004,6 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
                 rdma_event_str(cm_event->event));
         error_report("rdma_resolve_addr");
         rdma_ack_cm_event(cm_event);
-        ret = -EINVAL;
         goto err_resolve_get_addr;
     }
     rdma_ack_cm_event(cm_event);
@@ -1025,7 +1024,6 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
         ERROR(errp, "result not equal to event_route_resolved: %s",
                         rdma_event_str(cm_event->event));
         rdma_ack_cm_event(cm_event);
-        ret = -EINVAL;
         goto err_resolve_get_addr;
     }
     rdma_ack_cm_event(cm_event);
@@ -1040,7 +1038,7 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
 err_resolve_create_id:
     rdma_destroy_event_channel(rdma->channel);
     rdma->channel = NULL;
-    return ret;
+    return -1;
 }
 
 /*
@@ -2695,7 +2693,7 @@ static int qemu_rdma_dest_init(RDMAContext *rdma, Error **errp)
     port_str[15] = '\0';
 
     ret = rdma_getaddrinfo(rdma->host, port_str, NULL, &res);
-    if (ret < 0) {
+    if (ret) {
         ERROR(errp, "could not rdma_getaddrinfo address %s", rdma->host);
         goto err_dest_init_bind_addr;
     }
@@ -2739,7 +2737,7 @@ static int qemu_rdma_dest_init(RDMAContext *rdma, Error **errp)
     rdma_destroy_event_channel(rdma->channel);
     rdma->channel = NULL;
     rdma->error_state = ret;
-    return ret;
+    return -1;
 
 }