When IPF detects an overlapping or duplicate fragment, drop it instead
of marking its CT state invalid and returning it to the conntrack batch.
This aligns with the Linux kernel, which discards such fragments during
IP reassembly rather than forwarding them separately.
Assisted-by: composer-2.5-fast, Cursor
Fixes: 4ea96698f667 ("Userspace datapath: Add fragmentation handling.")
Signed-off-by: Eli Britstein <[email protected]>
---
lib/ipf.c | 8 +++----
tests/ofproto-dpif.at | 52 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+), 4 deletions(-)
diff --git a/lib/ipf.c b/lib/ipf.c
index d836b8824..185d6432e 100644
--- a/lib/ipf.c
+++ b/lib/ipf.c
@@ -823,8 +823,8 @@ ipf_is_frag_duped(const struct ipf_frag *frag_list, int
last_inuse_idx,
}
/* Adds a fragment to a list of fragments, if the fragment is not a
- * duplicate. If the fragment is a duplicate, that fragment is marked
- * invalid to avoid the work that conntrack would do to mark the fragment
+ * duplicate. If the fragment is a duplicate, the fragment is dropped
+ * to avoid the work that conntrack would do to mark the fragment
* as invalid, which it will in all cases. */
static bool
ipf_process_frag(struct ipf *ipf, struct ipf_list *ipf_list,
@@ -852,8 +852,8 @@ ipf_process_frag(struct ipf *ipf, struct ipf_list *ipf_list,
}
} else {
ipf_count(ipf, v6, IPF_NFRAGS_OVERLAP);
- pkt->md.ct_state = CS_INVALID;
- return false;
+ dp_packet_delete(pkt);
+ return true;
}
return true;
}
diff --git a/tests/ofproto-dpif.at b/tests/ofproto-dpif.at
index ee6ac873d..5308b3008 100644
--- a/tests/ofproto-dpif.at
+++ b/tests/ofproto-dpif.at
@@ -5669,6 +5669,58 @@ CHECK_COVERAGE([dpif_netdev_output_grow_queues], [1])
OVS_VSWITCHD_STOP
AT_CLEANUP
+AT_SETUP([ofproto-dpif - fragment handling - drop duplicate fragment])
+OVS_VSWITCHD_START
+add_of_ports --pcap br0 1 90
+
+AT_DATA([flows.txt], [dnl
+table=0 in_port=90,ip actions=ct(commit),output:1
+])
+AT_CHECK([ovs-ofctl -O OpenFlow11 replace-flows br0 flows.txt])
+
+dnl Send the same fragment twice. It is a last fragment (MF=0) at offset 400,
+dnl so it bypasses the minimum fragment size check and is admitted, yet it
+dnl cannot complete reassembly on its own (bytes 0..399 are missing). The
+dnl second copy is a duplicate and must be dropped, rather than marked CT
+dnl invalid and returned to the datapath, so it is never forwarded.
+dnl
+dnl Last fragment carrying bytes 400..799 (MF clear).
+dnl Ethernet II, Src: 50:54:00:00:00:09, Dst: 50:54:00:00:00:0a
+dnl Type: IPv4 (0x0800)
+dnl Internet Protocol Version 4, Src: 10.1.1.1, Dst: 10.1.1.2
+dnl 0100 .... = Version: 4
+dnl .... 0101 = Header Length: 20 bytes (5)
+dnl Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
+dnl Total Length: 420
+dnl Identification: 0x0020 (32)
+dnl 000. .... = Flags: 0x0 (Last fragment)
+dnl ...0 0000 0011 0010 = Fragment Offset: 400
+dnl Time to Live: 64
+dnl Protocol: UDP (17)
+dnl Header Checksum: 0x62f3
+dnl Data (400 bytes)
+eth="50 54 00 00 00 0a 50 54 00 00 00 09 08 00"
+ip="45 00 01 a4 00 20 00 32 40 11 62 f3"
+addrs="0a 01 01 01 0a 01 01 02"
+data=$(printf '%0*d' 800 0)
+packet="${eth}${ip}${addrs}${data}"
+
+AT_CHECK([ovs-appctl netdev-dummy/receive p90 "$packet"])
+AT_CHECK([ovs-appctl netdev-dummy/receive p90 "$packet"])
+
+AT_CHECK([ovs-appctl dpctl/ipf-get-status -m \
+| grep -E 'v4 frags accepted:|v4 frags overlapped:'], [], [dnl
+ v4 frags accepted: 1
+ v4 frags overlapped: 1
+])
+
+dnl The duplicate fragment is dropped, not marked invalid and forwarded, so
+dnl nothing must be transmitted on the output port.
+AT_CHECK([test 0 = `ovs-ofctl parse-pcap p1-tx.pcap | wc -l`])
+
+OVS_VSWITCHD_STOP
+AT_CLEANUP
+
AT_SETUP([ofproto-dpif - handling of malformed TCP packets])
OVS_VSWITCHD_START
add_of_ports br0 1 90
--
2.43.0
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