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if_pflog: fix packet length

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There were two issues with the new pflog packet length.
The first is that the length is expected to be a multiple of
sizeof(long), but we'd assumed it had to be a multiple of
sizeof(uint32_t).

The second is that there's some broken software out there (such as
Wireshark) that makes incorrect assumptions about the amount of padding.
That is, Wireshark assumes there's always three bytes of padding, rather
than however much is needed to get to a multiple of sizeof(long).

Fix this by adding extra padding, and a fake field to maintain
Wireshark's assumption.

Reported by:	Ozkan KIRIK <ozkan.kirik@gmail.com>
Tested by:	Ozkan KIRIK <ozkan.kirik@gmail.com>
MFC after:	1 week
Sponsored by:	Rubicon Communications, LLC ("Netgate")
Differential Revision:	https://reviews.freebsd.org/D33236
This commit is contained in:
Kristof Provost 2021-12-02 08:22:34 +01:00
parent 98470f0e0b
commit 6d4baa0d01
2 changed files with 7 additions and 3 deletions
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8
sys/net/if_pflog.h
View File

@ -31,6 +31,8 @@
#ifndef _NET_IF_PFLOG_H_
#define _NET_IF_PFLOG_H_
#include <net/bpf.h>
#define PFLOGIFS_MAX 16
#define PFLOG_RULESET_NAME_SIZE 16
@ -51,11 +53,13 @@ struct pfloghdr {
u_int8_t dir;
u_int8_t pad[3];
u_int32_t ridentifier;
u_int8_t reserve; /* Appease broken software like Wireshark. */
u_int8_t pad2[3];
};
#define PFLOG_HDRLEN sizeof(struct pfloghdr)
#define PFLOG_HDRLEN BPF_WORDALIGN(offsetof(struct pfloghdr, pad2))
/* minus pad, also used as a signature */
#define PFLOG_REAL_HDRLEN offsetof(struct pfloghdr, pad)
#define PFLOG_REAL_HDRLEN offsetof(struct pfloghdr, pad2)
#ifdef _KERNEL
struct pf_rule;

2
sys/netpfil/pf/if_pflog.c
View File

@ -215,7 +215,7 @@ pflog_packet(struct pfi_kkif *kif, struct mbuf *m, sa_family_t af, u_int8_t dir,
return (0);
bzero(&hdr, sizeof(hdr));
hdr.length = PFLOG_HDRLEN;
hdr.length = PFLOG_REAL_HDRLEN;
hdr.af = af;
hdr.action = rm->action;
hdr.reason = reason;