Generate cleaner code for "host", "net" and "gateway".

Following the same logic as for DECnet in commit 6f8a28c earlier, take
the link-layer protocol value out of any recursion gen_hostop() and
gen_hostop6() might do, instead just call gen_linktype() beforehand
exactly once.  In gen_host6() join two equivalent cases together for
clarity.

For ARP-capable DLTs this improves SNR in the unoptimized filter
programs of:

* "arp (host|net)"
* "ip (host|net)"
* "ip6 (host|net)"
* "rarp (host|net)"
* "(host|net)" (which is a logical OR of the above four)
* "arp gateway" (which is a superset of "not arp host")
* "ip gateway" (which is a superset of "not ip host")
* "rarp gateway" (which is a superset of "not rarp host")
* "gateway" (which is a logical OR of the above three)

For DLTs with a relatively simple structure this change makes the
unoptimized filter program for most of the above primitives the same as
the optimized one.  For IEEE 802.11 and ARCnet there is now fewer
instructions and less work to do for the optimizer.

Author: infrastation

gencode.c

@@ -659,10 +659,10 @@ static struct block *gen_linktype(compiler_state_t *, bpf_u_int32);
 static struct block *gen_snap(compiler_state_t *, bpf_u_int32, bpf_u_int32);
 static struct block *gen_llc_linktype(compiler_state_t *, bpf_u_int32);
 static struct block *gen_hostop(compiler_state_t *, bpf_u_int32, bpf_u_int32,
-    int, bpf_u_int32, u_int, u_int);
+    int, u_int, u_int);
 #ifdef INET6
 static struct block *gen_hostop6(compiler_state_t *, struct in6_addr *,
-    struct in6_addr *, int, bpf_u_int32, u_int, u_int);
+    struct in6_addr *, int, u_int, u_int);
 #endif
 static struct block *gen_ahostop(compiler_state_t *, const uint8_t, int);
 static struct block *gen_ehostop(compiler_state_t *, const u_char *, int);
@@ -4174,7 +4174,7 @@ gen_llc_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
 
 static struct block *
 gen_hostop(compiler_state_t *cstate, bpf_u_int32 addr, bpf_u_int32 mask,
-    int dir, bpf_u_int32 ll_proto, u_int src_off, u_int dst_off)
+    int dir, u_int src_off, u_int dst_off)
 {
 	struct block *b0, *b1;
 	u_int offset;
@@ -4190,15 +4190,15 @@ gen_hostop(compiler_state_t *cstate, bpf_u_int32 addr, bpf_u_int32 mask,
 		break;
 
 	case Q_AND:
-		b0 = gen_hostop(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
-		b1 = gen_hostop(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
+		b0 = gen_hostop(cstate, addr, mask, Q_SRC, src_off, dst_off);
+		b1 = gen_hostop(cstate, addr, mask, Q_DST, src_off, dst_off);
 		gen_and(b0, b1);
 		return b1;
 
 	case Q_DEFAULT:
 	case Q_OR:
-		b0 = gen_hostop(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
-		b1 = gen_hostop(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
+		b0 = gen_hostop(cstate, addr, mask, Q_SRC, src_off, dst_off);
+		b1 = gen_hostop(cstate, addr, mask, Q_DST, src_off, dst_off);
 		gen_or(b0, b1);
 		return b1;
 
@@ -4230,17 +4230,13 @@ gen_hostop(compiler_state_t *cstate, bpf_u_int32 addr, bpf_u_int32 mask,
 		abort();
 		/*NOTREACHED*/
 	}
-	b0 = gen_linktype(cstate, ll_proto);
-	b1 = gen_mcmp(cstate, OR_LINKPL, offset, BPF_W, addr, mask);
-	gen_and(b0, b1);
-	return b1;
+	return gen_mcmp(cstate, OR_LINKPL, offset, BPF_W, addr, mask);
 }
 
 #ifdef INET6
 static struct block *
 gen_hostop6(compiler_state_t *cstate, struct in6_addr *addr,
-    struct in6_addr *mask, int dir, bpf_u_int32 ll_proto, u_int src_off,
-    u_int dst_off)
+    struct in6_addr *mask, int dir, u_int src_off, u_int dst_off)
 {
 	struct block *b0, *b1;
 	u_int offset;
@@ -4266,15 +4262,15 @@ gen_hostop6(compiler_state_t *cstate, struct in6_addr *addr,
 		break;
 
 	case Q_AND:
-		b0 = gen_hostop6(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
-		b1 = gen_hostop6(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
+		b0 = gen_hostop6(cstate, addr, mask, Q_SRC, src_off, dst_off);
+		b1 = gen_hostop6(cstate, addr, mask, Q_DST, src_off, dst_off);
 		gen_and(b0, b1);
 		return b1;
 
 	case Q_DEFAULT:
 	case Q_OR:
-		b0 = gen_hostop6(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
-		b1 = gen_hostop6(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
+		b0 = gen_hostop6(cstate, addr, mask, Q_SRC, src_off, dst_off);
+		b1 = gen_hostop6(cstate, addr, mask, Q_DST, src_off, dst_off);
 		gen_or(b0, b1);
 		return b1;
 
@@ -4316,8 +4312,6 @@ gen_hostop6(compiler_state_t *cstate, struct in6_addr *addr,
 	gen_and(b0, b1);
 	b0 = gen_mcmp(cstate, OR_LINKPL, offset + 0, BPF_W, ntohl(a[0]), ntohl(m[0]));
 	gen_and(b0, b1);
-	b0 = gen_linktype(cstate, ll_proto);
-	gen_and(b0, b1);
 	return b1;
 }
 #endif
@@ -5182,13 +5176,22 @@ gen_host(compiler_state_t *cstate, bpf_u_int32 addr, bpf_u_int32 mask,
 		bpf_error(cstate, "link-layer modifier applied to %s", typestr);
 
 	case Q_IP:
-		return gen_hostop(cstate, addr, mask, dir, ETHERTYPE_IP, 12, 16);
+		b0 = gen_linktype(cstate, ETHERTYPE_IP);
+		b1 = gen_hostop(cstate, addr, mask, dir, 12, 16);
+		gen_and(b0, b1);
+		return b1;
 
 	case Q_RARP:
-		return gen_hostop(cstate, addr, mask, dir, ETHERTYPE_REVARP, 14, 24);
+		b0 = gen_linktype(cstate, ETHERTYPE_REVARP);
+		b1 = gen_hostop(cstate, addr, mask, dir, 14, 24);
+		gen_and(b0, b1);
+		return b1;
 
 	case Q_ARP:
-		return gen_hostop(cstate, addr, mask, dir, ETHERTYPE_ARP, 14, 24);
+		b0 = gen_linktype(cstate, ETHERTYPE_ARP);
+		b1 = gen_hostop(cstate, addr, mask, dir, 14, 24);
+		gen_and(b0, b1);
+		return b1;
 
 	case Q_SCTP:
 		bpf_error(cstate, "'sctp' modifier applied to %s", typestr);
@@ -5309,6 +5312,7 @@ static struct block *
 gen_host6(compiler_state_t *cstate, struct in6_addr *addr,
     struct in6_addr *mask, int proto, int dir, int type)
 {
+	struct block *b0, *b1;
 	const char *typestr;
 
 	if (type == Q_NET)
@@ -5319,7 +5323,11 @@ gen_host6(compiler_state_t *cstate, struct in6_addr *addr,
 	switch (proto) {
 
 	case Q_DEFAULT:
-		return gen_host6(cstate, addr, mask, Q_IPV6, dir, type);
+	case Q_IPV6:
+		b0 = gen_linktype(cstate, ETHERTYPE_IPV6);
+		b1 = gen_hostop6(cstate, addr, mask, dir, 8, 24);
+		gen_and(b0, b1);
+		return b1;
 
 	case Q_LINK:
 		bpf_error(cstate, "link-layer modifier applied to ip6 %s", typestr);
@@ -5369,9 +5377,6 @@ gen_host6(compiler_state_t *cstate, struct in6_addr *addr,
 	case Q_MOPDL:
 		bpf_error(cstate, "'mopdl' modifier applied to ip6 %s", typestr);
 
-	case Q_IPV6:
-		return gen_hostop6(cstate, addr, mask, dir, ETHERTYPE_IPV6, 8, 24);
-
 	case Q_ICMPV6:
 		bpf_error(cstate, "'icmp6' modifier applied to ip6 %s", typestr);