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| author |   Eric Dumazet <edumazet@google.com> | 2013-08-18 19:08:07 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2013-08-20 15:05:04 -0700 |
| commit | 734d2725db879f3f6fcdc2b1d2a5deae105f5e95 (patch) | |
| tree | 44648101fe8a2960add4c7d3b690f3fbcaac8841 | |
| parent | vhost: Include linux/uio.h instead of linux/socket.h (diff) | |
| download | linux-dev-734d2725db879f3f6fcdc2b1d2a5deae105f5e95.tar.xz linux-dev-734d2725db879f3f6fcdc2b1d2a5deae105f5e95.zip | |
ipv4: raise IP_MAX_MTU to theoretical limit
As discussed last year [1], there is no compelling reason
to limit IPv4 MTU to 0xFFF0, while real limit is 0xFFFF
[1] : http://marc.info/?l=linux-netdev&m=135607247609434&w=2
Willem raised this issue again because some of our internal
regression tests broke after lo mtu being set to 65536.
IP_MTU reports 0xFFF0, and the test attempts to send a RAW datagram of
mtu + 1 bytes, expecting the send() to fail, but it does not.
Alexey raised interesting points about TCP MSS, that should be addressed
in follow-up patches in TCP stack if needed, as someone could also set
an odd mtu anyway.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/route.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index e805481eff72..727f4365bcdf 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -112,7 +112,8 @@ #define RT_FL_TOS(oldflp4) \ ((oldflp4)->flowi4_tos & (IPTOS_RT_MASK | RTO_ONLINK)) -#define IP_MAX_MTU 0xFFF0 +/* IPv4 datagram length is stored into 16bit field (tot_len) */ +#define IP_MAX_MTU 0xFFFF #define RT_GC_TIMEOUT (300*HZ) @@ -1227,10 +1228,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst) mtu = 576; } - if (mtu > IP_MAX_MTU) - mtu = IP_MAX_MTU; - - return mtu; + return min_t(unsigned int, mtu, IP_MAX_MTU); } static struct fib_nh_exception *find_exception(struct fib_nh *nh, __be32 daddr) |