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net: Do not overwrite if_vlan's PCP

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In commit c7cffd65c5 the function ether_8021q_frame() was slightly
refactored to use pointer of struct ether_8021q_tag as parameter qtag to
include the new option proto.

It is wrong to write to qtag->pcp as it will effectively change the memory
that qtag points to. Unfortunately the transmit routine of if_vlan parses
pointer of the member ifv_qtag of its softc which stores vlan interface's
PCP internally, when transmitting mbufs that contains PCP the vlan
interface's PCP will get overwritten.

Fix by operating on a local copy of qtag->pcp. Also mark 'struct ether_8021q_tag'
as const so that compilers can pick up such kind of bug.

PR:	273304
Reviewed by:	kp
Fixes:	c7cffd65c5 Add support for stacked VLANs (IEEE 802.1ad, AKA Q-in-Q)
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D39505
This commit is contained in:
Zhenlei Huang 2023-08-23 17:48:12 +08:00
parent d18c845f99
commit 838c8c4786
2 changed files with 5 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sys/net/ethernet.h
View File

@ -446,7 +446,7 @@ void ether_vlan_mtap(struct bpf_if *, struct mbuf *,
void *, u_int);
struct mbuf *ether_vlanencap_proto(struct mbuf *, uint16_t, uint16_t);
bool ether_8021q_frame(struct mbuf **mp, struct ifnet *ife,
struct ifnet *p, struct ether_8021q_tag *);
struct ifnet *p, const struct ether_8021q_tag *);
void ether_gen_addr(struct ifnet *ifp, struct ether_addr *hwaddr);
static __inline struct mbuf *ether_vlanencap(struct mbuf *m, uint16_t tag)

7
sys/net/if_ethersubr.c
View File

@ -1400,11 +1400,12 @@ SYSCTL_INT(_net_link_vlan, OID_AUTO, mtag_pcp, CTLFLAG_RW | CTLFLAG_VNET,
bool
ether_8021q_frame(struct mbuf **mp, struct ifnet *ife, struct ifnet *p,
struct ether_8021q_tag *qtag)
const struct ether_8021q_tag *qtag)
{
struct m_tag *mtag;
int n;
uint16_t tag;
uint8_t pcp = qtag->pcp;
static const char pad[8]; /* just zeros */
/*
@ -1437,7 +1438,7 @@ ether_8021q_frame(struct mbuf **mp, struct ifnet *ife, struct ifnet *p,
* If PCP is set in mbuf, use it
*/
if ((*mp)->m_flags & M_VLANTAG) {
qtag->pcp = EVL_PRIOFTAG((*mp)->m_pkthdr.ether_vtag);
pcp = EVL_PRIOFTAG((*mp)->m_pkthdr.ether_vtag);
}
/*
@ -1451,7 +1452,7 @@ ether_8021q_frame(struct mbuf **mp, struct ifnet *ife, struct ifnet *p,
MTAG_8021Q_PCP_OUT, NULL)) != NULL)
tag = EVL_MAKETAG(qtag->vid, *(uint8_t *)(mtag + 1), 0);
else
tag = EVL_MAKETAG(qtag->vid, qtag->pcp, 0);
tag = EVL_MAKETAG(qtag->vid, pcp, 0);
if ((p->if_capenable & IFCAP_VLAN_HWTAGGING) &&
(qtag->proto == ETHERTYPE_VLAN)) {
(*mp)->m_pkthdr.ether_vtag = tag;