selftests: net: fix/improve ip_defrag selftest

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>

diff --git a/tools/testing/selftests/net/ip_defrag.c b/tools/testing/selftests/net/ip_defrag.c
index 61ae2782388e9d0921b06a4589c5d5662cb02e8e..5d56cc0838f627b44afc0ce225bdb2330fbcbe2a 100644 (file)
--- 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 f34672796044952a9a7b7b02496ac08ed29bd885..7dd79a9efb1772945f7b9415d080e0fec5f55a71 100755 (executable)
--- 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"