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-rw-r--r--include/net/ip.h1
-rw-r--r--net/ipv4/devinet.c2
-rw-r--r--net/ipv4/igmp.c24
-rw-r--r--net/ipv4/ip_tunnel.c4
4 files changed, 19 insertions, 12 deletions
diff --git a/include/net/ip.h b/include/net/ip.h
index 9896f46cbbf1..af8addbaa3c1 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -34,6 +34,7 @@
#include <net/flow_dissector.h>
#define IPV4_MAX_PMTU 65535U /* RFC 2675, Section 5.1 */
+#define IPV4_MIN_MTU 68 /* RFC 791 */
struct sock;
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index a4573bccd6da..7a93359fbc72 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1428,7 +1428,7 @@ skip:
static bool inetdev_valid_mtu(unsigned int mtu)
{
- return mtu >= 68;
+ return mtu >= IPV4_MIN_MTU;
}
static void inetdev_send_gratuitous_arp(struct net_device *dev,
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index d1f8f302dbf3..50448a220a1f 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -404,16 +404,17 @@ static int grec_size(struct ip_mc_list *pmc, int type, int gdel, int sdel)
}
static struct sk_buff *add_grhead(struct sk_buff *skb, struct ip_mc_list *pmc,
- int type, struct igmpv3_grec **ppgr)
+ int type, struct igmpv3_grec **ppgr, unsigned int mtu)
{
struct net_device *dev = pmc->interface->dev;
struct igmpv3_report *pih;
struct igmpv3_grec *pgr;
- if (!skb)
- skb = igmpv3_newpack(dev, dev->mtu);
- if (!skb)
- return NULL;
+ if (!skb) {
+ skb = igmpv3_newpack(dev, mtu);
+ if (!skb)
+ return NULL;
+ }
pgr = skb_put(skb, sizeof(struct igmpv3_grec));
pgr->grec_type = type;
pgr->grec_auxwords = 0;
@@ -436,12 +437,17 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc,
struct igmpv3_grec *pgr = NULL;
struct ip_sf_list *psf, *psf_next, *psf_prev, **psf_list;
int scount, stotal, first, isquery, truncate;
+ unsigned int mtu;
if (pmc->multiaddr == IGMP_ALL_HOSTS)
return skb;
if (ipv4_is_local_multicast(pmc->multiaddr) && !net->ipv4.sysctl_igmp_llm_reports)
return skb;
+ mtu = READ_ONCE(dev->mtu);
+ if (mtu < IPV4_MIN_MTU)
+ return skb;
+
isquery = type == IGMPV3_MODE_IS_INCLUDE ||
type == IGMPV3_MODE_IS_EXCLUDE;
truncate = type == IGMPV3_MODE_IS_EXCLUDE ||
@@ -462,7 +468,7 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc,
AVAILABLE(skb) < grec_size(pmc, type, gdeleted, sdeleted)) {
if (skb)
igmpv3_sendpack(skb);
- skb = igmpv3_newpack(dev, dev->mtu);
+ skb = igmpv3_newpack(dev, mtu);
}
}
first = 1;
@@ -498,12 +504,12 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc,
pgr->grec_nsrcs = htons(scount);
if (skb)
igmpv3_sendpack(skb);
- skb = igmpv3_newpack(dev, dev->mtu);
+ skb = igmpv3_newpack(dev, mtu);
first = 1;
scount = 0;
}
if (first) {
- skb = add_grhead(skb, pmc, type, &pgr);
+ skb = add_grhead(skb, pmc, type, &pgr, mtu);
first = 0;
}
if (!skb)
@@ -538,7 +544,7 @@ empty_source:
igmpv3_sendpack(skb);
skb = NULL; /* add_grhead will get a new one */
}
- skb = add_grhead(skb, pmc, type, &pgr);
+ skb = add_grhead(skb, pmc, type, &pgr, mtu);
}
}
if (pgr)
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index fe6fee728ce4..5ddb1cb52bd4 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -349,8 +349,8 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
dev->needed_headroom = t_hlen + hlen;
mtu -= (dev->hard_header_len + t_hlen);
- if (mtu < 68)
- mtu = 68;
+ if (mtu < IPV4_MIN_MTU)
+ mtu = IPV4_MIN_MTU;
return mtu;
}