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selftests: net: fix/improve ip_defrag selftest
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Commit ade4464 ("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>
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Peter Oskolkov authored and David S. Miller committed Jan 4, 2019
1 parent f87118d commit 3271a48
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Showing 2 changed files with 95 additions and 10 deletions.
96 changes: 87 additions & 9 deletions tools/testing/selftests/net/ip_defrag.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -239,33 +240,83 @@ 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;
fraghdr->ip6f_offlg = htons(offset / 8 | IP6_MF);
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++;
Expand All @@ -275,14 +326,21 @@ 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;
}
}

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;

Expand All @@ -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. */
Expand Down
9 changes: 8 additions & 1 deletion tools/testing/selftests/net/ip_defrag.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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() {
Expand All @@ -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

Expand All @@ -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"

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