bpf write filter, and lock

1 files changed, 54 insertions, 1 deletions

diff --git a/sbin/dhclient/bpf.c b/sbin/dhclient/bpf.c
index 886e988ce4e..131a88f743d 100644
--- a/sbin/dhclient/bpf.c
+++ b/sbin/dhclient/bpf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.c,v 1.12 2004/05/04 22:23:01 mickey Exp $	*/
+/*	$OpenBSD: bpf.c,v 1.13 2004/05/05 14:28:58 deraadt Exp $	*/
 
 /* BPF socket interface code, originally contributed by Archie Cobbs. */
 
@@ -129,6 +129,46 @@ struct bpf_insn dhcp_bpf_filter[] = {
 
 int dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn);
 
+/*
+ * Packet write filter program:
+ * 'ip and udp and src port bootps and dst port (bootps or bootpc)'
+ */
+struct bpf_insn dhcp_bpf_wfilter[] = {
+	BPF_STMT(BPF_LD + BPF_B + BPF_IND, 14),
+	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (IPVERSION << 4) + 5, 0, 12),
+
+	/* Make sure this is an IP packet... */
+	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
+	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 10),
+
+	/* Make sure it's a UDP packet... */
+	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
+	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 8),
+
+	/* Make sure this isn't a fragment... */
+	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
+	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 6, 0),	/* patched */
+
+	/* Get the IP header length... */
+	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
+
+	/* Make sure it's from the right port... */
+	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
+	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 68, 0, 3),
+
+	/* Make sure it is to the right ports ... */
+	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
+	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1),
+
+	/* If we passed all the tests, ask for the whole packet. */
+	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
+
+	/* Otherwise, drop it. */
+	BPF_STMT(BPF_RET+BPF_K, 0),
+};
+
+int dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn);
+
 void
 if_register_receive(struct interface_info *info)
 {
@@ -179,6 +219,19 @@ if_register_receive(struct interface_info *info)
 
 	if (ioctl(info->rfdesc, BIOCSETF, &p) < 0)
 		error("Can't install packet filter program: %m");
+
+	/* Set up the bpf write filter program structure. */
+	p.bf_len = dhcp_bpf_wfilter_len;
+	p.bf_insns = dhcp_bpf_wfilter;
+
+	if (dhcp_bpf_wfilter[7].k == 0x1fff)
+		dhcp_bpf_wfilter[7].k = htons(IP_MF|IP_OFFMASK);
+
+	if (ioctl(info->rfdesc, BIOCSETWF, &p) < 0)
+		error("Can't install write filter program: %m");
+
+	if (ioctl(info->rfdesc, BIOCLOCK, NULL) < 0)
+		error("Cannot lock bpf");
 }
 
 ssize_t