Make Netgraph compile with Clang.

Clang disallows structs with variable length arrays to be nested inside
other structs, because this is in violation with ISO C99. Even though we
can keep bugging the LLVM folks about this issue, we'd better just fix
our code to not do this. This code seems to be the only code in the
entire source tree that does this.

I haven't tested this patch by using the kernel modules in question, but
Diane Bruce and I have compared disassembled versions of these kernel
modules. We would have expected them to be exactly the same, but due to
randomness in the register allocator and reordering of instructions,
there were some minor differences.

Approved by:	julian

sys/netgraph/atm/ng_ccatm.h

@@ -166,7 +166,6 @@ struct ngm_ccatm_portlist {
 
 struct ccatm_op {
 	uint32_t	op;	/* request code */
-	u_char		data[];
 };
 
 #endif

sys/netgraph/ng_pppoe.c

@@ -290,7 +290,7 @@ static	int	pppoe_send_event(sessp sp, enum cmd cmdid);
 static __inline const struct pppoe_tag*
 next_tag(const struct pppoe_hdr* ph)
 {
-	return (const struct pppoe_tag*)(((const char*)&ph->tag[0])
+	return (const struct pppoe_tag*)(((const char*)(ph + 1))
 	    + ntohs(ph->length));
 }
 
@@ -303,7 +303,7 @@ static const struct pppoe_tag*
 get_tag(const struct pppoe_hdr* ph, uint16_t idx)
 {
 	const char *const end = (const char *)next_tag(ph);
-	const struct pppoe_tag *pt = &ph->tag[0];
+	const struct pppoe_tag *pt = (const void *)(ph + 1);
 	const char *ptn;
 
 	/*
@@ -381,7 +381,7 @@ make_packet(sessp sp) {
 	    ("%s: called from wrong state", __func__));
 	CTR2(KTR_NET, "%20s: called %d", __func__, sp->Session_ID);
 
-	dp = (char *)wh->ph.tag;
+	dp = (char *)(&wh->ph + 1);
 	for (count = 0, tag = sp->neg->tags;
 	    ((count < sp->neg->numtags) && (count < NUMTAGS));
 	    tag++, count++) {
@@ -434,12 +434,12 @@ pppoe_match_svc(node_p node, const struct pppoe_tag *tag)
 		if (neg->service_len != ntohs(tag->tag_len))
 			continue;
 
-		if (strncmp(tag->tag_data, neg->service.data,
+		if (strncmp((const char *)(tag + 1), neg->service.data,
 		    ntohs(tag->tag_len)) == 0)
 			break;
 	}
 	CTR3(KTR_NET, "%20s: matched %p for %s", __func__,
-	    sp?sp->hook:NULL, tag->tag_data);
+	    sp?sp->hook:NULL, (const char *)(tag + 1));
 
 	return (sp?sp->hook:NULL);
 }
@@ -583,7 +583,7 @@ pppoe_finduniq(node_p node, const struct pppoe_tag *tag)
 	hook_p	hook = NULL;
 	union uniq uniq;
 
-	bcopy(tag->tag_data, uniq.bytes, sizeof(void *));
+	bcopy(tag + 1, uniq.bytes, sizeof(void *));
 	/* Cycle through all known hooks. */
 	LIST_FOREACH(hook, &node->nd_hooks, hk_hooks) {
 		/* Skip any nonsession hook. */
@@ -1100,7 +1100,7 @@ send_acname(sessp sp, const struct pppoe_tag *tag)
 
 	sts = (struct ngpppoe_sts *)msg->data;
 	tlen = min(NG_HOOKSIZ - 1, ntohs(tag->tag_len));
-	strncpy(sts->hook, tag->tag_data, tlen);
+	strncpy(sts->hook, (const char *)(tag + 1), tlen);
 	sts->hook[tlen] = '\0';
 	NG_SEND_MSG_ID(error, NG_HOOK_NODE(sp->hook), msg, sp->creator, 0);
 
@@ -1438,7 +1438,8 @@ ng_pppoe_rcvdata_ether(hook_p hook, item_p item)
 					break;
 				}
 				if (neg->ac_name_len != htons(tag->tag_len) ||
-				    strncmp(neg->ac_name.data, tag->tag_data,
+				    strncmp(neg->ac_name.data,
+				    (const char *)(tag + 1),
 				    neg->ac_name_len) != 0) {
 					break;
 				}
@@ -1767,10 +1768,10 @@ ng_pppoe_disconnect(hook_p hook)
 				 * Add a General error message and adjust
 				 * sizes.
 				 */
-				tag = wh->ph.tag;
+				tag = (void *)(&wh->ph + 1);
 				tag->tag_type = PTT_GEN_ERR;
 				tag->tag_len = htons((u_int16_t)msglen);
-				strncpy(tag->tag_data, SIGNOFF, msglen);
+				strncpy((char *)(tag + 1), SIGNOFF, msglen);
 				m->m_pkthdr.len = (m->m_len += sizeof(*tag) +
 				    msglen);
 				wh->ph.length = htons(sizeof(*tag) + msglen);
@@ -1859,7 +1860,7 @@ scan_tags(sessp	sp, const struct pppoe_hdr* ph)
 {
 	const char *const end = (const char *)next_tag(ph);
 	const char *ptn;
-	const struct pppoe_tag *pt = &ph->tag[0];
+	const struct pppoe_tag *pt = (const void *)(ph + 1);
 
 	/*
 	 * Keep processing tags while a tag header will still fit.

sys/netgraph/ng_pppoe.h

@@ -201,7 +201,6 @@ struct ngpppoe_sts {
 struct pppoe_tag {
 	u_int16_t tag_type;
 	u_int16_t tag_len;
-	char tag_data[];
 }__packed;
 
 struct pppoe_hdr{
@@ -210,7 +209,6 @@ struct pppoe_hdr{
 	u_int8_t code;
 	u_int16_t sid;
 	u_int16_t length;
-	struct pppoe_tag tag[];
 }__packed;