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dhclient: remove patching of static values in BPF programs

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Reviewed by:	markj
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D31502
This commit is contained in:
Franco Fichtner 2021-08-19 09:08:59 -04:00 committed by Mark Johnston
parent 1a4d7030bb
commit 5851803f4b
1 changed files with 11 additions and 28 deletions
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39
sbin/dhclient/bpf.c
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@ -105,7 +105,7 @@ if_register_bpf(struct interface_info *info, int flags)
* Packet write filter program:
* 'ip and udp and src port bootps and dst port (bootps or bootpc)'
*/
static struct bpf_insn dhcp_bpf_wfilter[] = {
static const 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),
@ -119,18 +119,18 @@ static struct bpf_insn dhcp_bpf_wfilter[] = {
/* 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 */
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, IP_MF|IP_OFFMASK, 6, 0),
/* 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),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, LOCAL_PORT, 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),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, REMOTE_PORT, 0, 1),
/* If we passed all the tests, ask for the whole packet. */
BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
@ -139,8 +139,6 @@ static struct bpf_insn dhcp_bpf_wfilter[] = {
BPF_STMT(BPF_RET+BPF_K, 0),
};
static int dhcp_bpf_wfilter_len = nitems(dhcp_bpf_wfilter);
void
if_register_send(struct interface_info *info)
{
@ -161,11 +159,8 @@ if_register_send(struct interface_info *info)
error("Kernel BPF version out of range - recompile dhcpd!");
/* 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);
p.bf_insns = __DECONST(struct bpf_insn *, dhcp_bpf_wfilter);
p.bf_len = nitems(dhcp_bpf_wfilter);
if (ioctl(info->wfdesc, BIOCSETWF, &p) < 0)
error("Can't install write filter program: %m");
@ -190,11 +185,8 @@ if_register_send(struct interface_info *info)
/*
* Packet filter program...
*
* XXX: Changes to the filter program may require changes to the
* constant offsets used in if_register_send to patch the BPF program!
*/
static struct bpf_insn dhcp_bpf_filter[] = {
static const struct bpf_insn dhcp_bpf_filter[] = {
/* 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, 8),
@ -205,14 +197,14 @@ static struct bpf_insn dhcp_bpf_filter[] = {
/* 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, 4, 0),
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, IP_MF|IP_OFFMASK, 4, 0),
/* Get the IP header length... */
BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
/* Make sure it's to the right port... */
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), /* patch */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, LOCAL_PORT, 0, 1),
/* If we passed all the tests, ask for the whole packet. */
BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
@ -221,8 +213,6 @@ static struct bpf_insn dhcp_bpf_filter[] = {
BPF_STMT(BPF_RET+BPF_K, 0),
};
static int dhcp_bpf_filter_len = nitems(dhcp_bpf_filter);
void
if_register_receive(struct interface_info *info)
{
@ -263,15 +253,8 @@ if_register_receive(struct interface_info *info)
info->rbuf_len = 0;
/* Set up the bpf filter program structure. */
p.bf_len = dhcp_bpf_filter_len;
p.bf_insns = dhcp_bpf_filter;
/* Patch the server port into the BPF program...
*
* XXX: changes to filter program may require changes to the
* insn number(s) used below!
*/
dhcp_bpf_filter[8].k = LOCAL_PORT;
p.bf_insns = __DECONST(struct bpf_insn *, dhcp_bpf_filter);
p.bf_len = nitems(dhcp_bpf_filter);
if (ioctl(info->rfdesc, BIOCSETF, &p) < 0)
error("Can't install packet filter program: %m");