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test: net: add IP defragmentation duplicate-fragment regression test

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Add a unit test for the IP datagram reassembler (CONFIG_IP_DEFRAG) that
covers the duplicate-last-fragment scenario.

Without the fix the last fragment will re-trigger datagram delivery,
increasing udp_rx_count to 2 and effectively failing the test; with it
applied the test passes with udp_rx_count == 1.

Signed-off-by: Mateusz Furdyna <mateusz.furdyna@nokia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Mateusz Furdyna
2026-06-23 13:13:16 +02:00
committed by Jerome Forissier
parent b1aec609bb
commit 8382c2ad52
2 changed files with 83 additions and 0 deletions
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test/dm/Makefile
+1
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@@ -76,6 +76,7 @@ obj-$(CONFIG_MULTIPLEXER) += mux-emul.o
obj-$(CONFIG_MUX_MMIO) += mux-mmio.o
obj-y += fdtdec.o
obj-$(CONFIG_MTD_RAW_NAND) += nand.o
obj-$(CONFIG_IP_DEFRAG) += net_defrag.o
obj-$(CONFIG_UT_DM) += nop.o
obj-y += ofnode.o
obj-y += ofread.o
test/dm/net_defrag.c
+82
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@@ -0,0 +1,82 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Regression test for IP fragment reassembly.
*
* The test drives the real RX path via net_process_received_packet(). Final IP
* fragment (MF=0) is duplicated, crafted payload triggers redelivery of the datagram,
* which fails the test for the unfixed code.
*/
#include <net.h>
#include <string.h>
#include <test/ut.h>
#include <dm/test.h>
#define FRAG_LEN (8)
#define PAYLOAD_OFFSET (ETHER_HDR_SIZE + IP_HDR_SIZE)
#define FRAME_LEN (PAYLOAD_OFFSET + FRAG_LEN)
static int udp_rx_count;
static void defrag_udp_handler(uchar *pkt, unsigned int dport,
struct in_addr sip, unsigned int sport,
unsigned int len)
{
udp_rx_count++;
}
static int build_frag(uchar *buf, u16 off_flags, const u16 *payload)
{
struct ethernet_hdr *et = (struct ethernet_hdr *)buf;
struct ip_udp_hdr *ip = (struct ip_udp_hdr *)(buf + ETHER_HDR_SIZE);
memset(buf, 0, FRAME_LEN);
et->et_protlen = htons(PROT_IP);
ip->ip_hl_v = 0x45;
ip->ip_len = htons(IP_HDR_SIZE + FRAG_LEN);
ip->ip_id = htons(0x4321);
ip->ip_off = htons(off_flags);
ip->ip_ttl = 64;
ip->ip_p = IPPROTO_UDP;
/* Broadcast destination is accepted regardless of net_ip. */
ip->ip_dst.s_addr = 0xffffffff;
ip->ip_sum = compute_ip_checksum(ip, IP_HDR_SIZE);
memcpy(buf + PAYLOAD_OFFSET, payload, FRAG_LEN);
return FRAME_LEN;
}
static int dm_test_net_ip_defrag_dup_last(struct unit_test_state *uts)
{
rxhand_f *saved_handler = net_get_udp_handler();
uchar frame[FRAME_LEN];
/* UDP header, carried by first fragment. */
u16 udp_hdr[4] = { htons(5000), htons(5001),
htons(UDP_HDR_SIZE + FRAG_LEN), 0 };
/*
* Second fragment's payload doubles as a fake hole
* {last_byte >= FRAG_LEN, next_hole = 0, prev_hole = 0}, so that the
* buggy code re-reading it on a duplicate re-delivers the datagram.
*/
u16 frag_b[4] = { 2 * FRAG_LEN, 0, 0, 0 };
udp_rx_count = 0;
net_set_udp_handler(defrag_udp_handler);
/* UDP header, offset 0, MF=1; then data, offset 1, MF=0 */
net_process_received_packet(frame, build_frag(frame, IP_FLAGS_MFRAG, udp_hdr));
net_process_received_packet(frame, build_frag(frame, 1, frag_b));
ut_asserteq(1, udp_rx_count);
/* Duplicate the final fragment: UDP datagram must not be delivered again. */
net_process_received_packet(frame, build_frag(frame, 1, frag_b));
ut_asserteq(1, udp_rx_count);
net_set_udp_handler(saved_handler);
return 0;
}
DM_TEST(dm_test_net_ip_defrag_dup_last, 0);