diff options
| author | Willem de Bruijn <willemb@google.com> | 2016-11-02 11:02:16 -0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-11-03 15:41:11 -0400 |
| commit | 70ecc24841326396a827deb55c3fefac582a729d (patch) | |
| tree | a581934fe1a71bd2f820c64e20f7800aec264841 /include/uapi | |
| parent | 1b99e5e854d4de2d795c4dbed7cc59c65ae372fe (diff) | |
ipv4: add IP_RECVFRAGSIZE cmsg
The IP stack records the largest fragment of a reassembled packet
in IPCB(skb)->frag_max_size. When reading a datagram or raw packet
that arrived fragmented, expose the value to allow applications to
estimate receive path MTU.
Tested:
Sent data over a veth pair of which the source has a small mtu.
Sent data using netcat, received using a dedicated process.
Verified that the cmsg IP_RECVFRAGSIZE is returned only when
data arrives fragmented, and in that cases matches the veth mtu.
ip link add veth0 type veth peer name veth1
ip netns add from
ip netns add to
ip link set dev veth1 netns to
ip netns exec to ip addr add dev veth1 192.168.10.1/24
ip netns exec to ip link set dev veth1 up
ip link set dev veth0 netns from
ip netns exec from ip addr add dev veth0 192.168.10.2/24
ip netns exec from ip link set dev veth0 up
ip netns exec from ip link set dev veth0 mtu 1300
ip netns exec from ethtool -K veth0 ufo off
dd if=/dev/zero bs=1 count=1400 2>/dev/null > payload
ip netns exec to ./recv_cmsg_recvfragsize -4 -u -p 6000 &
ip netns exec from nc -q 1 -u 192.168.10.1 6000 < payload
using github.com/wdebruij/kerneltools/blob/master/tests/recvfragsize.c
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/linux/in.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h index eaf94919291a..4e557f4e9553 100644 --- a/include/uapi/linux/in.h +++ b/include/uapi/linux/in.h @@ -117,6 +117,7 @@ struct in_addr { #define IP_NODEFRAG 22 #define IP_CHECKSUM 23 #define IP_BIND_ADDRESS_NO_PORT 24 +#define IP_RECVFRAGSIZE 25 /* IP_MTU_DISCOVER values */ #define IP_PMTUDISC_DONT 0 /* Never send DF frames */ |