MINOR: Add TO/FROM_SET flags to struct stream_interface

[WT: it will make sense to remove SN_FRT_ADDR_SET and to use these
  flags everywhere instead ]
diff --git a/include/types/stream_interface.h b/include/types/stream_interface.h
index 8f35d64..dae36ef 100644
--- a/include/types/stream_interface.h
+++ b/include/types/stream_interface.h
@@ -73,6 +73,8 @@
 	SI_FL_INDEP_STR  = 0x0040,  /* independant streams = don't update rex on write */
 	SI_FL_NOLINGER   = 0x0080,  /* may close without lingering. One-shot. */
 	SI_FL_SRC_ADDR   = 0x1000,  /* get the source ip/port with getsockname */
+	SI_FL_TO_SET     = 0x2000,  /* addr.to is set */
+	SI_FL_FROM_SET   = 0x4000,  /* addr.from is set */
 };
 
 /* target types */
diff --git a/src/frontend.c b/src/frontend.c
index 12dc2c8..35c3ef3 100644
--- a/src/frontend.c
+++ b/src/frontend.c
@@ -54,6 +54,7 @@
 
 	if (get_original_dst(s->si[0].fd, (struct sockaddr_in *)&s->si[0].addr.to, &namelen) == -1)
 		getsockname(s->si[0].fd, (struct sockaddr *)&s->si[0].addr.to, &namelen);
+	s->si[0].flags |= SI_FL_TO_SET;
 	s->flags |= SN_FRT_ADDR_SET;
 }
 
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 6324196..39ef26b 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -443,6 +443,7 @@
 		if (getsockname(fd, (struct sockaddr *)&si->addr.from, &addrlen) == -1) {
 			Warning("Cannot get source address for logging.\n");
 		}
+		si->flags |= SI_FL_FROM_SET;
 	}
 
 	fdtab[fd].owner = si;