pf: copy out rather than m_pullup() in pf_test_eth_rule()

Don't change the mbuf chain layout. We've encountered alignment issues
in the tcp syncookie code on armv7, which appear to result from the
m_pullup() here.

eg:
	Kernel page fault with the following non-sleepable locks held:
	exclusive sleep mutex tcp_sc_head (tcp_sc_head) r = 0 (0xdbfc4058) locked @ /usr/src/sys/netinet/tcp_syncache.c:534
	exclusive rw tcpinp (tcpinp) r = 0 (0xded8ee28) locked @ /usr/src/sys/netinet/in_pcb.c:2436
	stack backtrace:
	#0 0xc0421480 at witness_debugger+0x6c
	#1 0xc0422514 at witness_warn+0x430
	#2 0xc07d8830 at abort_handler+0x1d8
	#3 0xc07bb1cc at exception_exit+0
	#4 0xc06320bc at syncookie_lookup+0x4c
	#5 0xc0630cb0 at syncache_expand+0xc4
	#6 0xc061be00 at tcp_input+0x11b0
	#7 0xc058f8b4 at ip_input+0x264
	#8 0xc04f5ca8 at netisr_dispatch_src+0xec
	#9 0xc04d39e8 at ether_demux+0x204
	#10 0xc04d5088 at ether_nh_input+0x3e8
	#11 0xc04f5ca8 at netisr_dispatch_src+0xec
	#12 0xc04d3f10 at ether_input+0xfc
	#13 0xc07fa750 at mvneta_rxtxth_intr+0x2b4
	#14 0xc037f784 at ithread_loop+0x1cc
	#15 0xc037c4c8 at fork_exit+0xa0
	#16 0xc07bb15c at swi_exit+0
	Fatal kernel mode data abort: 'Alignment Fault' on read
	trapframe: 0xc7d28980
	FSR=00000001, FAR=dbf7886e, spsr=60000013
	r0 =00000025, r1 =00000001, r2 =c7d2894c, r3 =60000013
	r4 =c7d28a58, r5 =c7d28bc8, r6 =dbf7886a, r7 =dbfc4058
	r8 =dbfc4058, r9 =c7d28b98, r10=c7d28bfc, r11=c7d28a30
	r12=20000000, ssp=c7d28a10, slr=c06320bc, pc =c06320bc

Redmine:	8287

sys/netpfil/pf/pf.c

@@ -3820,6 +3820,8 @@ pf_match_eth_addr(const uint8_t *a, const struct pf_keth_rule_addr *r)
 static int
 pf_test_eth_rule(int dir, struct pfi_kkif *kif, struct mbuf **m0)
 {
+	struct ip ip;
+	struct ip6_hdr ip6;
 	struct mbuf *m = *m0;
 	struct ether_header *e;
 	struct pf_keth_rule *r, *rm, *a = NULL;
@@ -3862,31 +3864,17 @@ pf_test_eth_rule(int dir, struct pfi_kkif *kif, struct mbuf **m0)
 
 	switch (proto) {
 	case ETHERTYPE_IP: {
-		struct ip *ip;
-		m = m_pullup(m, sizeof(struct ether_header) +
-		    sizeof(struct ip));
-		if (m == NULL) {
-			*m0 = NULL;
-			return (PF_DROP);
-		}
+		m_copydata(m, sizeof(struct ether_header), sizeof(ip), (caddr_t)&ip);
 		af = AF_INET;
-		ip = mtodo(m, sizeof(struct ether_header));
-		src = (struct pf_addr *)&ip->ip_src;
-		dst = (struct pf_addr *)&ip->ip_dst;
+		src = (struct pf_addr *)&ip.ip_src;
+		dst = (struct pf_addr *)&ip.ip_dst;
 		break;
 	}
 	case ETHERTYPE_IPV6: {
-		struct ip6_hdr *ip6;
-		m = m_pullup(m, sizeof(struct ether_header) +
-		    sizeof(struct ip6_hdr));
-		if (m == NULL) {
-			*m0 = NULL;
-			return (PF_DROP);
-		}
+		m_copydata(m, sizeof(struct ether_header), sizeof(ip6), (caddr_t)&ip6);
 		af = AF_INET6;
-		ip6 = mtodo(m, sizeof(struct ether_header));
-		src = (struct pf_addr *)&ip6->ip6_src;
-		dst = (struct pf_addr *)&ip6->ip6_dst;
+		src = (struct pf_addr *)&ip6.ip6_src;
+		dst = (struct pf_addr *)&ip6.ip6_dst;
 		break;
 	}
 	}