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dhclient: these ancient patches make no sense to me 

Imported into FreeBSD from OpenBSD 3.7.  Imported in 2004 from
ISC DHCP...  Looks like the patching was part of templating for
different things, sort of see:

https://gitlab.isc.org/isc-projects/dhcp/-/blob/master/common/bpf.c

At least we know the BPF filter values should be given in host
order and apparently the whole thing keeps working.

While here enable the IP_MF bit reading which seems to be cool.
This commit is contained in:
Franco Fichtner 2021-06-10 15:11:50 +02:00
parent 12f2fc5598
commit bb99396c1f
1 changed files with 5 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
sbin/dhclient/bpf.c
View File

@ -121,7 +121,7 @@ static struct bpf_insn dhcp_bpf_wfilter[] = {
/* Make sure this isn't a fragment... */
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 20),
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 12, 0), /* patched */
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, IP_MF|IP_OFFMASK, 12, 0),
/* Get the IP header length... */
BPF_STMT(BPF_MISC + BPF_TXA, 0),
@ -134,11 +134,11 @@ static struct bpf_insn dhcp_bpf_wfilter[] = {
/* 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),
@ -172,9 +172,6 @@ if_register_send(struct interface_info *info)
p.bf_len = dhcp_bpf_wfilter_len;
p.bf_insns = dhcp_bpf_wfilter;
if (dhcp_bpf_wfilter[11].k == 0x1fff)
dhcp_bpf_wfilter[11].k = htons(IP_MF|IP_OFFMASK);
if (ioctl(info->wfdesc, BIOCSETWF, &p) < 0)
error("Can't install write filter program: %m");
@ -228,7 +225,7 @@ static struct bpf_insn dhcp_bpf_filter[] = {
/* Make sure this isn't a fragment... */
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 20),
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 10, 0),
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, IP_MF|IP_OFFMASK, 10, 0),
/* Get the IP header length... */
BPF_STMT(BPF_MISC + BPF_TXA, 0),
@ -241,7 +238,7 @@ static struct bpf_insn dhcp_bpf_filter[] = {
/* 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),
@ -295,13 +292,6 @@ if_register_receive(struct interface_info *info)
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[21].k = LOCAL_PORT;
if (ioctl(info->rfdesc, BIOCSETF, &p) < 0)
error("Can't install packet filter program: %m");