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dhclient: support VID 0 (no vlan) decapsulation

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VLAN ID 0 is supposed to be interpreted as having no VLAN with a bit of
priority on the side, but the kernel is not able to decapsulate this on
the fly so dhclient needs to take care of it.

Reviewed by:	markj
MFC after:	3 weeks
Differential Revision:	https://reviews.freebsd.org/D31515
This commit is contained in:
Franco Fichtner 2022-02-14 09:43:29 -05:00 committed by Mark Johnston
parent 99589993ce
commit abf5bff71d
2 changed files with 48 additions and 8 deletions
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53
sbin/dhclient/bpf.c
View file

@ -5,6 +5,7 @@
/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2021 Franco Fichtner <franco@opnsense.org>
* Copyright (c) 1995, 1996, 1998, 1999
* The Internet Software Consortium. All rights reserved.
*
@ -187,20 +188,58 @@ if_register_send(struct interface_info *info)
* Packet filter program...
*/
static const struct bpf_insn dhcp_bpf_filter[] = {
/* Use relative index (0) for IP packet... */
BPF_STMT(BPF_LDX + BPF_W + BPF_IMM, 0),
/*
* Test whether this is a VLAN packet...
*
* In case the server packet is using a VLAN ID
* of 0, meaning an untagged priority was set, the
* response shall be read and replied to.
*/
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 12),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_VLAN, 0, 4),
/* Test whether it has a VID of 0 */
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
BPF_STMT(BPF_ALU + BPF_AND + BPF_K, EVL_VLID_MASK),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 17),
/* Correct the relative index for VLAN packet (4)... */
BPF_STMT(BPF_LDX + BPF_W + BPF_IMM, 4),
/* 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),
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 12),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 14),
/* 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, 6),
BPF_STMT(BPF_LD + BPF_B + BPF_IND, 23),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 12),
/* Make sure this isn't a fragment... */
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, IP_MF|IP_OFFMASK, 4, 0),
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 20),
BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, IP_MF|IP_OFFMASK, 10, 0),
/* Get the IP header length... */
/*
* Get the IP header length...
*
* To find the correct position of the IP header
* length field store the index (0 or 4) in the
* accumulator and compare it with 0.
*/
BPF_STMT(BPF_MISC + BPF_TXA, 0),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 2),
/* Store IP header length of IP packet in index. */
BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
/* Skip over following VLAN handling instruction. */
BPF_JUMP(BPF_JMP + BPF_JA, 1, 0, 0),
/* Store IP header length of VLAN packet in index. */
BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 18),
/* Add IP header length to previous relative index. */
BPF_STMT(BPF_ALU + BPF_ADD + BPF_X, 0),
/* Move result back to index to reach UDP header below. */
BPF_STMT(BPF_MISC + BPF_TAX, 0),
/* Make sure it's to the right port... */
BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),

3
sbin/dhclient/packet.c
View file

@ -157,7 +157,8 @@ decode_hw_header(unsigned char *buf, int bufix, struct hardware *from)
from->htype = ARPHRD_ETHER;
from->hlen = sizeof(eh.ether_shost);
return (sizeof(eh));
return (sizeof(eh) + (ntohs(eh.ether_type) == ETHERTYPE_VLAN ?
ETHER_VLAN_ENCAP_LEN : 0));
}
ssize_t