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authorWillem de Bruijn <willemb@google.com>2016-11-02 11:02:16 -0400
committerDavid S. Miller <davem@davemloft.net>2016-11-03 15:41:11 -0400
commit70ecc24841326396a827deb55c3fefac582a729d (patch)
treea581934fe1a71bd2f820c64e20f7800aec264841 /net/ipv4/ip_sockglue.c
parentMerge branch 'stmmac-OXNAS' (diff)
downloadlinux-dev-70ecc24841326396a827deb55c3fefac582a729d.tar.xz
linux-dev-70ecc24841326396a827deb55c3fefac582a729d.zip
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 'net/ipv4/ip_sockglue.c')
-rw-r--r--net/ipv4/ip_sockglue.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b8a2d63d1fb8..ecbaae200131 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -97,6 +97,17 @@ static void ip_cmsg_recv_retopts(struct msghdr *msg, struct sk_buff *skb)
put_cmsg(msg, SOL_IP, IP_RETOPTS, opt->optlen, opt->__data);
}
+static void ip_cmsg_recv_fragsize(struct msghdr *msg, struct sk_buff *skb)
+{
+ int val;
+
+ if (IPCB(skb)->frag_max_size == 0)
+ return;
+
+ val = IPCB(skb)->frag_max_size;
+ put_cmsg(msg, SOL_IP, IP_RECVFRAGSIZE, sizeof(val), &val);
+}
+
static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
int tlen, int offset)
{
@@ -218,6 +229,9 @@ void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
if (flags & IP_CMSG_CHECKSUM)
ip_cmsg_recv_checksum(msg, skb, tlen, offset);
+
+ if (flags & IP_CMSG_RECVFRAGSIZE)
+ ip_cmsg_recv_fragsize(msg, skb);
}
EXPORT_SYMBOL(ip_cmsg_recv_offset);
@@ -614,6 +628,7 @@ static int do_ip_setsockopt(struct sock *sk, int level,
case IP_MULTICAST_LOOP:
case IP_RECVORIGDSTADDR:
case IP_CHECKSUM:
+ case IP_RECVFRAGSIZE:
if (optlen >= sizeof(int)) {
if (get_user(val, (int __user *) optval))
return -EFAULT;
@@ -726,6 +741,14 @@ static int do_ip_setsockopt(struct sock *sk, int level,
}
}
break;
+ case IP_RECVFRAGSIZE:
+ if (sk->sk_type != SOCK_RAW && sk->sk_type != SOCK_DGRAM)
+ goto e_inval;
+ if (val)
+ inet->cmsg_flags |= IP_CMSG_RECVFRAGSIZE;
+ else
+ inet->cmsg_flags &= ~IP_CMSG_RECVFRAGSIZE;
+ break;
case IP_TOS: /* This sets both TOS and Precedence */
if (sk->sk_type == SOCK_STREAM) {
val &= ~INET_ECN_MASK;
@@ -1357,6 +1380,9 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
case IP_CHECKSUM:
val = (inet->cmsg_flags & IP_CMSG_CHECKSUM) != 0;
break;
+ case IP_RECVFRAGSIZE:
+ val = (inet->cmsg_flags & IP_CMSG_RECVFRAGSIZE) != 0;
+ break;
case IP_TOS:
val = inet->tos;
break;