From: Matteo Croce mcroce@redhat.com
[ Upstream commit 258bbb1b0e594ad5f5652cb526b3c63e6a7fad3d ]
The ICMP implementation currently replies to an ICMP time exceeded message (type 11) with an ICMP host unreachable message (type 3, code 1).
However, time exceeded messages can either represent "time to live exceeded in transit" (code 0) or "fragment reassembly time exceeded" (code 1).
Unconditionally replying to "fragment reassembly time exceeded" with host unreachable messages might cause unjustified connection resets which are now easily triggered as UFO has been removed, because, in turn, sending large buffers triggers IP fragmentation.
The issue can be easily reproduced by running a lot of UDP streams which is likely to trigger IP fragmentation:
# start netserver in the test namespace ip netns add test ip netns exec test netserver
# create a VETH pair ip link add name veth0 type veth peer name veth0 netns test ip link set veth0 up ip -n test link set veth0 up
for i in $(seq 20 29); do # assign addresses to both ends ip addr add dev veth0 192.168.$i.1/24 ip -n test addr add dev veth0 192.168.$i.2/24
# start the traffic netperf -L 192.168.$i.1 -H 192.168.$i.2 -t UDP_STREAM -l 0 & done
# wait send_data: data send error: No route to host (errno 113) netperf: send_omni: send_data failed: No route to host
We need to differentiate instead: if fragment reassembly time exceeded is reported, we need to silently drop the packet, if time to live exceeded is reported, maintain the current behaviour. In both cases increment the related error count "icmpInTimeExcds".
While at it, fix a typo in a comment, and convert the if statement into a switch to mate it more readable.
Signed-off-by: Matteo Croce mcroce@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@verizon.com --- net/ipv4/icmp.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 681e33998e03..3c1570d3e22f 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -782,7 +782,7 @@ static bool icmp_tag_validation(int proto) }
/* - * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and + * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and * ICMP_PARAMETERPROB. */
@@ -810,7 +810,8 @@ static bool icmp_unreach(struct sk_buff *skb) if (iph->ihl < 5) /* Mangled header, drop. */ goto out_err;
- if (icmph->type == ICMP_DEST_UNREACH) { + switch (icmph->type) { + case ICMP_DEST_UNREACH: switch (icmph->code & 15) { case ICMP_NET_UNREACH: case ICMP_HOST_UNREACH: @@ -846,8 +847,16 @@ static bool icmp_unreach(struct sk_buff *skb) } if (icmph->code > NR_ICMP_UNREACH) goto out; - } else if (icmph->type == ICMP_PARAMETERPROB) + break; + case ICMP_PARAMETERPROB: info = ntohl(icmph->un.gateway) >> 24; + break; + case ICMP_TIME_EXCEEDED: + __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS); + if (icmph->code == ICMP_EXC_FRAGTIME) + goto out; + break; + }
/* * Throw it at our lower layers