Fix address of packed member warnings.

Includes https://github.com/google/packetdrill/commit/c5013aa73b973689a2af92f49e28f1695e905e60.

gtests/net/packetdrill/Makefile.Darwin

 packetdrill-ext-libs := -lpcap
-CFLAGS = -D__APPLE_USE_RFC_3542 -Wall -Werror -Wno-unknown-warning-option -Wno-address-of-packed-member
+CFLAGS = -D__APPLE_USE_RFC_3542 -Wall -Werror -Wno-unknown-warning-option
 LDFLAGS =
 ifneq ("$(wildcard /usr/lib/libsctp.dylib)","")
     packetdrill-ext-libs += -lsctp

gtests/net/packetdrill/Makefile.FreeBSD

@@ -2,6 +2,6 @@ ARCH != uname -p
 packetdrill-ext-libs := -lprocstat -lutil -lkvm -lelf -lpthread -lpcap
 CFLAGS = -Wall -Werror
 .if ${ARCH} != "powerpc" && ${ARCH} != "powerpc64"
-  CFLAGS += -Wno-unknown-warning-option -Wno-address-of-packed-member
+  CFLAGS += -Wno-unknown-warning-option
 .endif
 .include "Makefile.common"

gtests/net/packetdrill/Makefile.Linux

 packetdrill-ext-libs := -lpthread -lrt -ldl -lsctp -static
-CFLAGS = -Wall -Werror -Wno-unknown-warning-option -Wno-address-of-packed-member
+CFLAGS = -Wall -Werror -Wno-unknown-warning-option
 include Makefile.common

gtests/net/packetdrill/Makefile.NetBSD

 packetdrill-ext-libs := -lpthread -lpcap
-CFLAGS = -Wall -Werror -Wno-unknown-warning-option -Wno-address-of-packed-member
+CFLAGS = -Wall -Werror -Wno-unknown-warning-option
 .include "Makefile.common"

gtests/net/packetdrill/Makefile.OpenBSD

 packetdrill-ext-libs := -lpthread -lpcap
-CFLAGS = -Wall -Werror -Wno-unknown-warning-option -Wno-address-of-packed-member
+CFLAGS = -Wall -Werror -Wno-unknown-warning-option
 .include "Makefile.common"

gtests/net/packetdrill/packet.h

@@ -26,9 +26,11 @@
 #ifndef __PACKET_H__
 #define __PACKET_H__
 
+#include <stddef.h>
+#include <sys/time.h>
+
 #include "types.h"
 
-#include <sys/time.h>
 #include "assert.h"
 #include "gre.h"
 #include "header.h"
@@ -422,7 +424,7 @@ static inline u32 *packet_echoed_sctp_v_tag(struct packet *packet, bool encapsul
 {
 	struct sctp_common_header *echoed_sctp = packet_echoed_sctp_header(packet, encapsulated);
 	assert(echoed_sctp);
-	u32 *v_tag = &(echoed_sctp->v_tag);
+	u32 *v_tag = (u32 *)((char *)echoed_sctp + offsetof(struct sctp_common_header, v_tag));
 	/* Check that the v_tag field is actually in the space we
 	 * reserved for the echoed prefix of the SCTP common header.
 	 */

gtests/net/packetdrill/run_packet.c

@@ -26,6 +26,7 @@
 
 #include <arpa/inet.h>
 #include <netinet/in.h>
+#include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
@@ -553,8 +554,12 @@ static int find_tcp_timestamp(struct packet *packet, char **error)
 	for (option = tcp_options_begin(packet, &iter); option != NULL;
 	     option = tcp_options_next(&iter, error))
 		if (option->kind == TCPOPT_TIMESTAMP) {
-			packet->tcp_ts_val = &(option->data.time_stamp.val);
-			packet->tcp_ts_ecr = &(option->data.time_stamp.ecr);
+			const size_t val_off = offsetof(struct tcp_option,
+			                                data.time_stamp.val);
+			const size_t ecr_off = offsetof(struct tcp_option,
+			                                data.time_stamp.ecr);
+			packet->tcp_ts_val = (__be32 *)((char *)option + val_off);
+			packet->tcp_ts_ecr = (__be32 *)((char *)option + ecr_off);
 		}
 	return *error ? STATUS_ERR : STATUS_OK;
 }