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For changing the MTU on tun/tap devices, it should not matter whether it

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is done via using ifconfig, which uses a SIOCSIFMTU ioctl() command, or
doing it using a TUNSIFINFO/TAPSIFINFO ioctl() command.
Without this patch, for IPv6 the new MTU is not used when creating routes.
Especially, when initiating TCP connections after increasing the MTU,
the old MTU is still used to compute the MSS.
Thanks to ae@ and bz@ for helping to improve the patch.

Reviewed by:		ae@, bz@
Approved by:		re (kib@)
MFC after:		1 week
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D17180
This commit is contained in:
Michael Tuexen 2018-09-29 13:01:23 +00:00
parent 275c893dab
commit 1687b1ab24
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=339012
4 changed files with 31 additions and 12 deletions
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3
sys/net/if.c
View File

@ -264,7 +264,6 @@ static int if_setflag(struct ifnet *, int, int, int *, int);
static int if_transmit(struct ifnet *ifp, struct mbuf *m);
static void if_unroute(struct ifnet *, int flag, int fam);
static void link_rtrequest(int, struct rtentry *, struct rt_addrinfo *);
static int ifhwioctl(u_long, struct ifnet *, caddr_t, struct thread *);
static int if_delmulti_locked(struct ifnet *, struct ifmultiaddr *, int);
static void do_link_state_change(void *, int);
static int if_getgroup(struct ifgroupreq *, struct ifnet *);
@ -2512,7 +2511,7 @@ ifr_data_get_ptr(void *ifrp)
/*
* Hardware specific interface ioctls.
*/
static int
int
ifhwioctl(u_long cmd, struct ifnet *ifp, caddr_t data, struct thread *td)
{
struct ifreq *ifr;

15
sys/net/if_tap.c
View File

@ -723,10 +723,12 @@ tapifstart(struct ifnet *ifp)
static int
tapioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag, struct thread *td)
{
struct ifreq ifr;
struct tap_softc *tp = dev->si_drv1;
struct ifnet *ifp = tp->tap_ifp;
struct tapinfo *tapp = NULL;
int f;
int error;
#if defined(COMPAT_FREEBSD6) || defined(COMPAT_FREEBSD5) || \
defined(COMPAT_FREEBSD4)
int ival;
@ -738,7 +740,18 @@ tapioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag, struct thread *td
if (ifp->if_type != tapp->type)
return (EPROTOTYPE);
mtx_lock(&tp->tap_mtx);
ifp->if_mtu = tapp->mtu;
if (ifp->if_mtu != tapp->mtu) {
strncpy(ifr.ifr_name, if_name(ifp), IFNAMSIZ);
ifr.ifr_mtu = tapp->mtu;
CURVNET_SET(ifp->if_vnet);
error = ifhwioctl(SIOCSIFMTU, ifp,
(caddr_t)&ifr, td);
CURVNET_RESTORE();
if (error) {
mtx_unlock(&tp->tap_mtx);
return (error);
}
}
ifp->if_baudrate = tapp->baudrate;
mtx_unlock(&tp->tap_mtx);
break;

23
sys/net/if_tun.c
View File

@ -662,24 +662,29 @@ static int
tunioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag,
struct thread *td)
{
int error;
struct ifreq ifr;
struct tun_softc *tp = dev->si_drv1;
struct tuninfo *tunp;
int error;
switch (cmd) {
case TUNSIFINFO:
tunp = (struct tuninfo *)data;
if (tunp->mtu < IF_MINMTU)
return (EINVAL);
if (TUN2IFP(tp)->if_mtu != tunp->mtu) {
error = priv_check(td, PRIV_NET_SETIFMTU);
if (error)
return (error);
}
if (TUN2IFP(tp)->if_type != tunp->type)
return (EPROTOTYPE);
mtx_lock(&tp->tun_mtx);
TUN2IFP(tp)->if_mtu = tunp->mtu;
if (TUN2IFP(tp)->if_mtu != tunp->mtu) {
strncpy(ifr.ifr_name, if_name(TUN2IFP(tp)), IFNAMSIZ);
ifr.ifr_mtu = tunp->mtu;
CURVNET_SET(TUN2IFP(tp)->if_vnet);
error = ifhwioctl(SIOCSIFMTU, TUN2IFP(tp),
(caddr_t)&ifr, td);
CURVNET_RESTORE();
if (error) {
mtx_unlock(&tp->tun_mtx);
return (error);
}
}
TUN2IFP(tp)->if_baudrate = tunp->baudrate;
mtx_unlock(&tp->tun_mtx);
break;

2
sys/net/if_var.h
View File

@ -760,6 +760,8 @@ int if_hw_tsomax_update(if_t ifp, struct ifnet_hw_tsomax *);
/* accessors for struct ifreq */
void *ifr_data_get_ptr(void *ifrp);
int ifhwioctl(u_long, struct ifnet *, caddr_t, struct thread *);
#ifdef DEVICE_POLLING
enum poll_cmd { POLL_ONLY, POLL_AND_CHECK_STATUS };