[PATCH nft 4/8] datatype: avoid cast-align warning with struct sockaddr result from getaddrinfo()

[Thomas Haller <thaller@redhat.com>]

With CC=clang we get

    datatype.c:625:11: error: cast from 'struct sockaddr *' to 'struct sockaddr_in *' increases required alignment from 2 to 4 [-Werror,-Wcast-align]
                    addr = ((struct sockaddr_in *)ai->ai_addr)->sin_addr;
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    datatype.c:690:11: error: cast from 'struct sockaddr *' to 'struct sockaddr_in6 *' increases required alignment from 2 to 4 [-Werror,-Wcast-align]
                    addr = ((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr;
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    datatype.c:826:11: error: cast from 'struct sockaddr *' to 'struct sockaddr_in *' increases required alignment from 2 to 4 [-Werror,-Wcast-align]
                    port = ((struct sockaddr_in *)ai->ai_addr)->sin_port;
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix that by casting to (void*) first. Also, add an assertion that the
type is as expected.

For inet_service_type_parse(), differentiate between AF_INET and
AF_INET6. It might not have been a problem in practice, because the
struct offsets of sin_port/sin6_port are identical.

Signed-off-by: Thomas Haller <thaller@redhat.com>
---
 src/datatype.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/datatype.c b/src/datatype.c
index a91b9cb793d5..4d0e44eeb500 100644
--- a/src/datatype.c
+++ b/src/datatype.c
@@ -622,7 +622,8 @@ static struct error_record *ipaddr_type_parse(struct parse_ctx *ctx,
 			return error(&sym->location,
 				     "Hostname resolves to multiple addresses");
 		}
-		addr = ((struct sockaddr_in *)ai->ai_addr)->sin_addr;
+		assert(ai->ai_addr->sa_family == AF_INET);
+		addr = ((struct sockaddr_in *) (void *) ai->ai_addr)->sin_addr;
 		freeaddrinfo(ai);
 	}
 
@@ -687,7 +688,9 @@ static struct error_record *ip6addr_type_parse(struct parse_ctx *ctx,
 			return error(&sym->location,
 				     "Hostname resolves to multiple addresses");
 		}
-		addr = ((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr;
+
+		assert(ai->ai_addr->sa_family == AF_INET6);
+		addr = ((struct sockaddr_in6 *)(void *)ai->ai_addr)->sin6_addr;
 		freeaddrinfo(ai);
 	}
 
@@ -823,7 +826,12 @@ static struct error_record *inet_service_type_parse(struct parse_ctx *ctx,
 			return error(&sym->location, "Could not resolve service: %s",
 				     gai_strerror(err));
 
-		port = ((struct sockaddr_in *)ai->ai_addr)->sin_port;
+		if (ai->ai_addr->sa_family == AF_INET)
+			port = ((struct sockaddr_in *)(void *)ai->ai_addr)->sin_port;
+		else {
+			assert(ai->ai_addr->sa_family == AF_INET6);
+			port = ((struct sockaddr_in6 *)(void *)ai->ai_addr)->sin6_port;
+		}
 		freeaddrinfo(ai);
 	}
 
-- 
2.41.0