[PATCH AUTOSEL 4.20 026/105] selftests: net: fix/improve ip_defrag selftest

Sasha Levin
2019-02-13T03:04:31Z

From: Peter Oskolkov <posk@google.com>

[ Upstream commit 3271a4821882a64214acc1bd7b173900ec70c9bf ]

Commit ade446403bfb ("net: ipv4: do not handle duplicate fragments as
overlapping") changed IPv4 defragmentation so that duplicate fragments,
as well as _some_ fragments completely covered by previously delivered
fragments, do not lead to the whole frag queue being discarded. This
makes the existing ip_defrag selftest flaky.

This patch
* makes sure that negative IPv4 defrag tests generate truly overlapping
fragments that trigger defrag queue drops;
* tests that duplicate IPv4 fragments do not trigger defrag queue drops;
* makes a couple of minor tweaks to the test aimed at increasing its code
coverage and reduce flakiness.

Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/net/ip_defrag.c | 96 +++++++++++++++++++++---
tools/testing/selftests/net/ip_defrag.sh | 9 ++-
2 files changed, 95 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/net/ip_defrag.c b/tools/testing/selftests/net/ip_defrag.c
index 61ae2782388e..5d56cc0838f6 100644
--- a/tools/testing/selftests/net/ip_defrag.c
+++ b/tools/testing/selftests/net/ip_defrag.c
@@ -203,6 +203,7 @@ static void send_udp_frags(int fd_raw, struct sockaddr *addr,
{
struct ip *iphdr = (struct ip *)ip_frame;
struct ip6_hdr *ip6hdr = (struct ip6_hdr *)ip_frame;
+ const bool ipv4 = !ipv6;
int res;
int offset;
int frag_len;
@@ -239,19 +240,53 @@ static void send_udp_frags(int fd_raw, struct sockaddr *addr,
iphdr->ip_sum = 0;
}

+ /* Occasionally test in-order fragments. */
+ if (!cfg_overlap && (rand() % 100 < 15)) {
+ offset = 0;
+ while (offset < (UDP_HLEN + payload_len)) {
+ send_fragment(fd_raw, addr, alen, offset, ipv6);
+ offset += max_frag_len;
+ }
+ return;
+ }
+
+ /* Occasionally test IPv4 "runs" (see net/ipv4/ip_fragment.c) */
+ if (ipv4 && !cfg_overlap && (rand() % 100 < 20) &&
+ (payload_len > 9 * max_frag_len)) {
+ offset = 6 * max_frag_len;
+ while (offset < (UDP_HLEN + payload_len)) {
+ send_fragment(fd_raw, addr, alen, offset, ipv6);
+ offset += max_frag_len;
+ }
+ offset = 3 * max_frag_len;
+ while (offset < 6 * max_frag_len) {
+ send_fragment(fd_raw, addr, alen, offset, ipv6);
+ offset += max_frag_len;
+ }
+ offset = 0;
+ while (offset < 3 * max_frag_len) {
+ send_fragment(fd_raw, addr, alen, offset, ipv6);
+ offset += max_frag_len;
+ }
+ return;
+ }
+
/* Odd fragments. */
offset = max_frag_len;
while (offset < (UDP_HLEN + payload_len)) {
send_fragment(fd_raw, addr, alen, offset, ipv6);
+ /* IPv4 ignores duplicates, so randomly send a duplicate. */
+ if (ipv4 && (1 == rand() % 100))
+ send_fragment(fd_raw, addr, alen, offset, ipv6);
offset += 2 * max_frag_len;
}

if (cfg_overlap) {
/* Send an extra random fragment. */
- offset = rand() % (UDP_HLEN + payload_len - 1);
- /* sendto() returns EINVAL if offset + frag_len is too small. */
if (ipv6) {
struct ip6_frag *fraghdr = (struct ip6_frag *)(ip_frame + IP6_HLEN);
+ /* sendto() returns EINVAL if offset + frag_len is too small. */
+ offset = rand() % (UDP_HLEN + payload_len - 1);
frag_len = max_frag_len + rand() % 256;
/* In IPv6 if !!(frag_len % 8), the fragment is dropped. */
frag_len &= ~0x7;
@@ -259,13 +294,29 @@ static void send_udp_frags(int fd_raw, struct sockaddr *addr,
ip6hdr->ip6_plen = htons(frag_len);
frag_len += IP6_HLEN;
} else {
- frag_len = IP4_HLEN + UDP_HLEN + rand() % 256;
+ /* In IPv4, duplicates and some fragments completely inside
+ * previously sent fragments are dropped/ignored. So
+ * random offset and frag_len can result in a dropped
+ * fragment instead of a dropped queue/packet. So we
+ * hard-code offset and frag_len.
+ *
+ * See ade446403bfb ("net: ipv4: do not handle duplicate
+ * fragments as overlapping").
+ */
+ if (max_frag_len * 4 < payload_len || max_frag_len < 16) {
+ /* not enough payload to play with random offset and frag_len. */
+ offset = 8;
+ frag_len = IP4_HLEN + UDP_HLEN + max_frag_len;
+ } else {
+ offset = rand() % (payload_len / 2);
+ frag_len = 2 * max_frag_len + 1 + rand() % 256;
+ }
iphdr->ip_off = htons(offset / 8 | IP4_MF);
iphdr->ip_len = htons(frag_len);
}
res = sendto(fd_raw, ip_frame, frag_len, 0, addr, alen);
if (res < 0)
- error(1, errno, "sendto overlap");
+ error(1, errno, "sendto overlap: %d", frag_len);
if (res != frag_len)
error(1, 0, "sendto overlap: %d vs %d", (int)res, frag_len);
frag_counter++;
@@ -275,6 +326,9 @@ static void send_udp_frags(int fd_raw, struct sockaddr *addr,
offset = 0;
while (offset < (UDP_HLEN + payload_len)) {
send_fragment(fd_raw, addr, alen, offset, ipv6);
+ /* IPv4 ignores duplicates, so randomly send a duplicate. */
+ if (ipv4 && (1 == rand() % 100))
+ send_fragment(fd_raw, addr, alen, offset, ipv6);
offset += 2 * max_frag_len;
}
}
@@ -282,7 +336,11 @@ static void send_udp_frags(int fd_raw, struct sockaddr *addr,
static void run_test(struct sockaddr *addr, socklen_t alen, bool ipv6)
{
int fd_tx_raw, fd_rx_udp;
- struct timeval tv = { .tv_sec = 0, .tv_usec = 10 * 1000 };
+ /* Frag queue timeout is set to one second in the calling script;
+ * socket timeout should be just a bit longer to avoid tests interfering
+ * with each other.
+ */
+ struct timeval tv = { .tv_sec = 1, .tv_usec = 10 };
int idx;
int min_frag_len = ipv6 ? 1280 : 8;

@@ -308,12 +366,32 @@ static void run_test(struct sockaddr *addr, socklen_t alen, bool ipv6)
payload_len += (rand() % 4096)) {
if (cfg_verbose)
printf("payload_len: %d\n", payload_len);
- max_frag_len = min_frag_len;
- do {
+
+ if (cfg_overlap) {
+ /* With overlaps, one send/receive pair below takes
+ * at least one second (== timeout) to run, so there
+ * is not enough test time to run a nested loop:
+ * the full overlap test takes 20-30 seconds.
+ */
+ max_frag_len = min_frag_len +
+ rand() % (1500 - FRAG_HLEN - min_frag_len);
send_udp_frags(fd_tx_raw, addr, alen, ipv6);
recv_validate_udp(fd_rx_udp);
- max_frag_len += 8 * (rand() % 8);
- } while (max_frag_len < (1500 - FRAG_HLEN) && max_frag_len <= payload_len);
+ } else {
+ /* Without overlaps, each packet reassembly (== one
+ * send/receive pair below) takes very little time to
+ * run, so we can easily afford more thourough testing
+ * with a nested loop: the full non-overlap test takes
+ * less than one second).
+ */
+ max_frag_len = min_frag_len;
+ do {
+ send_udp_frags(fd_tx_raw, addr, alen, ipv6);
+ recv_validate_udp(fd_rx_udp);
+ max_frag_len += 8 * (rand() % 8);
+ } while (max_frag_len < (1500 - FRAG_HLEN) &&
+ max_frag_len <= payload_len);
+ }
}

/* Cleanup. */
diff --git a/tools/testing/selftests/net/ip_defrag.sh b/tools/testing/selftests/net/ip_defrag.sh
index f34672796044..7dd79a9efb17 100755
--- a/tools/testing/selftests/net/ip_defrag.sh
+++ b/tools/testing/selftests/net/ip_defrag.sh
@@ -11,10 +11,17 @@ readonly NETNS="ns-$(mktemp -u XXXXXX)"
setup() {
ip netns add "${NETNS}"
ip -netns "${NETNS}" link set lo up
+
ip netns exec "${NETNS}" sysctl -w net.ipv4.ipfrag_high_thresh=9000000 >/dev/null 2>&1
ip netns exec "${NETNS}" sysctl -w net.ipv4.ipfrag_low_thresh=7000000 >/dev/null 2>&1
+ ip netns exec "${NETNS}" sysctl -w net.ipv4.ipfrag_time=1 >/dev/null 2>&1
+
ip netns exec "${NETNS}" sysctl -w net.ipv6.ip6frag_high_thresh=9000000 >/dev/null 2>&1
ip netns exec "${NETNS}" sysctl -w net.ipv6.ip6frag_low_thresh=7000000 >/dev/null 2>&1
+ ip netns exec "${NETNS}" sysctl -w net.ipv6.ip6frag_time=1 >/dev/null 2>&1
+
+ # DST cache can get full with a lot of frags, with GC not keeping up with the test.
+ ip netns exec "${NETNS}" sysctl -w net.ipv6.route.max_size=65536 >/dev/null 2>&1
}

cleanup() {
@@ -27,7 +34,6 @@ setup
echo "ipv4 defrag"
ip netns exec "${NETNS}" ./ip_defrag -4

-
echo "ipv4 defrag with overlaps"
ip netns exec "${NETNS}" ./ip_defrag -4o

@@ -37,3 +43,4 @@ ip netns exec "${NETNS}" ./ip_defrag -6
echo "ipv6 defrag with overlaps"
ip netns exec "${NETNS}" ./ip_defrag -6o

+echo "all tests done"
--
2.19.1