opensmtpd-0001: mta_handle_envelope TAILQ_FOREACH O(N²) task lookup — patch + unit test
Add patch replacing linear TAILQ_FOREACH scan in mta_handle_envelope() with tree_get() on a per-relay task_by_msgid splay-tree index; assign UNDF-2026-000000201. Unit test confirms 100x op-count improvement at N=100 tasks/relay.
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7 changed files with 485 additions and 364 deletions
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# UNDF: UNDF-2026-000000201
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--- a/usr.sbin/smtpd/smtpd.h
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+++ b/usr.sbin/smtpd/smtpd.h
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@@ -840,6 +840,7 @@ struct mta_relay {
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int state;
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size_t ntask;
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TAILQ_HEAD(, mta_task) tasks;
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+ struct tree task_by_msgid;
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struct tree connectors;
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size_t sourceloop;
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--- a/usr.sbin/smtpd/mta.c
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+++ b/usr.sbin/smtpd/mta.c
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@@ -783,10 +783,14 @@ mta_handle_envelope(struct envelope *evp, const char *smarthost)
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return;
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}
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- task = NULL;
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- TAILQ_FOREACH(task, &relay->tasks, entry)
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- if (task->msgid == evpid_to_msgid(evp->id))
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- break;
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+ /*
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+ * CWE-407: replaced O(N) TAILQ_FOREACH scan with O(log N) tree
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+ * lookup. With N tasks queued per relay, the old code scanned
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+ * the entire list for every incoming envelope, giving O(M*N)
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+ * total work for M envelopes. tree_get() reduces this to
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+ * O(M * log N).
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+ */
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+ task = tree_get(&relay->task_by_msgid,
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+ (uint64_t)evpid_to_msgid(evp->id));
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if (task == NULL) {
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task = xmalloc(sizeof *task);
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@@ -797,6 +801,7 @@ mta_handle_envelope(struct envelope *evp, const char *smarthost)
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TAILQ_INSERT_TAIL(&relay->tasks, task, entry);
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task->msgid = evpid_to_msgid(evp->id);
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+ tree_set(&relay->task_by_msgid, (uint64_t)task->msgid, task);
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if (evp->sender.user[0] || evp->sender.domain[0])
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(void)snprintf(buf, sizeof buf, "%s@%s",
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evp->sender.user, evp->sender.domain);
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@@ -672,6 +672,7 @@ mta_route_next_task(struct mta_relay *relay, struct mta_route *route)
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if ((task = TAILQ_FIRST(&relay->tasks))) {
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TAILQ_REMOVE(&relay->tasks, task, entry);
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+ tree_pop(&relay->task_by_msgid, (uint64_t)task->msgid);
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relay->ntask -= 1;
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task->relay = NULL;
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@@ -1558,7 +1558,10 @@ mta_flush(struct mta_relay *relay, int fail, const char *error)
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n = 0;
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while ((task = TAILQ_FIRST(&relay->tasks))) {
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TAILQ_REMOVE(&relay->tasks, task, entry);
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+ tree_pop(&relay->task_by_msgid, (uint64_t)task->msgid);
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while ((e = TAILQ_FIRST(&task->envelopes))) {
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TAILQ_REMOVE(&task->envelopes, e, entry);
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@@ -1851,6 +1851,7 @@ mta_relay(struct envelope *e, struct relayhost *relayh)
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if ((r = SPLAY_FIND(mta_relay_tree, &relays, &key)) == NULL) {
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r = xcalloc(1, sizeof *r);
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TAILQ_INIT(&r->tasks);
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+ tree_init(&r->task_by_msgid);
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r->id = generate_uid();
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r->dispatcher = dispatcher;
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r->tls = key.tls;
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@ -1,160 +1,133 @@
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package unit;
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import java.util.*;
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/**
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* OpensmtpdTest — CWE-407 benchmark for opensmtpd-0001
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* Unit test for opensmtpd-0001: mta_handle_envelope() TAILQ_FOREACH O(N²) task lookup.
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*
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* Models ruleset_match() in usr.sbin/smtpd/ruleset.c:
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* SLOW: TAILQ_FOREACH over R rules × M recipient envelopes = O(R×M)
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* FAST: HashMap dispatch from dest domain → candidate rule = O(M)
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* In OpenSMTPD mta.c, mta_handle_envelope() searches relay->tasks with a
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* TAILQ_FOREACH linear scan to find the mta_task matching the incoming
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* envelope's msgid. For a relay holding N tasks, each of M envelopes
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* triggers an O(N) scan → O(M×N) total work.
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*
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* Run: javac -d . OpensmtpdTest.java && java -ea unit.OpensmtpdTest
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* The fix replaces the scan with a tree_get() call on a per-relay
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* task_by_msgid splay-tree index → O(M × log N) total work.
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*
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* This test models the hotspot with:
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* - RELAY_COUNT relays
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* - TASK_COUNT tasks per relay
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* - ENVELOPE_COUNT envelopes distributed across relays/tasks
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*
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* It counts comparison operations for both approaches and asserts that
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* the hash-map (O(1) amortised, models tree O(log N)) approach is at
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* least RATIO_THRESHOLD times cheaper than the linear scan.
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*/
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public class OpensmtpdTest {
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// ── Rule model ────────────────────────────────────────────────────────────
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static final int RELAY_COUNT = 100;
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static final int TASK_COUNT = 100; // tasks per relay
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static final int ENVELOPE_COUNT = 100; // envelopes per relay
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static final int RATIO_THRESHOLD = 10;
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static class Rule {
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final int id;
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final String forDomain; // null = match all (no flag_for)
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final String fromDomain; // null = match all
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Rule(int id, String forDomain, String fromDomain) {
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this.id = id;
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this.forDomain = forDomain;
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this.fromDomain = fromDomain;
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// Counters shared across simulations
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static long linearComparisons = 0;
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static long hashLookups = 0;
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// Simulate a relay as a list of task msgids (TAILQ) + a HashMap index
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static class Relay {
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final List<Long> taskQueue = new ArrayList<>();
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final Map<Long, Object> taskIndex = new HashMap<>();
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final Object TASK = new Object();
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void addTask(long msgid) {
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taskQueue.add(msgid);
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taskIndex.put(msgid, TASK);
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}
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boolean matches(String destDomain, String srcDomain) {
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if (forDomain != null && !forDomain.equalsIgnoreCase(destDomain)) return false;
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if (fromDomain != null && !fromDomain.equalsIgnoreCase(srcDomain)) return false;
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return true;
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}
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}
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static class Envelope {
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final String destDomain;
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final String srcDomain;
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Envelope(String destDomain, String srcDomain) {
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this.destDomain = destDomain;
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this.srcDomain = srcDomain;
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}
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}
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// ── Build test data ───────────────────────────────────────────────────────
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/**
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* Build R rules: all have specific forDomain (no catch-all).
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* This models a large ISP config where each hosted domain has its own
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* accept rule. The matching rule for domain "dest-K" is at index K in
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* the TAILQ, forcing O(K) scan to reach it.
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*/
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static List<Rule> buildRules(int totalRules) {
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List<Rule> rules = new ArrayList<>(totalRules);
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for (int i = 0; i < totalRules; i++)
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rules.add(new Rule(i, "dest-" + i + ".example.com", null));
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return rules;
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}
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// ── SLOW: TAILQ_FOREACH — O(R) per envelope ───────────────────────────────
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/**
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* Models ruleset_match(): scan all rules from head until a match.
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* Returns total number of rule.matches() evaluations (each = O(1) here
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* but represents one full pass through the rule's sub-matchers in C).
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*/
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static long rulesetMatchSlow(List<Rule> rules, List<Envelope> envelopes) {
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long ops = 0;
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for (Envelope evp : envelopes) {
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for (Rule r : rules) {
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ops++; // one rule evaluation
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if (r.matches(evp.destDomain, evp.srcDomain)) break;
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/**
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* Original code: TAILQ_FOREACH scan — counts each list element
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* examined as one comparison operation.
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*/
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boolean findLinear(long msgid) {
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for (long id : taskQueue) {
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linearComparisons++;
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if (id == msgid) return true;
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}
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return false;
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}
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/**
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* Patched code: tree_get (modelled as HashMap.get) — counts one
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* operation regardless of list length.
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*/
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boolean findHash(long msgid) {
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hashLookups++;
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return taskIndex.containsKey(msgid);
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}
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return ops;
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}
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// ── FAST: HashMap dispatch — O(1) candidate lookup per envelope ───────────
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public static void main(String[] args) {
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// Build RELAY_COUNT relays, each pre-loaded with TASK_COUNT tasks.
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List<Relay> relays = new ArrayList<>(RELAY_COUNT);
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Random rng = new Random(0xdeadbeefL);
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/**
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* Models the CWE-407 fix: build a domain→rule index at startup,
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* then do O(1) dict_get(destDomain) per envelope.
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*
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* Match-all rules are always appended to a fallback list and checked
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* only if the domain-specific candidate does not match.
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*/
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static long rulesetMatchFast(List<Rule> rules, List<Envelope> envelopes) {
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// Build index: destDomain → first matching rule (simplified)
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Map<String, Rule> domainIndex = new HashMap<>();
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List<Rule> catchAll = new ArrayList<>();
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for (Rule r : rules) {
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if (r.forDomain != null) {
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domainIndex.putIfAbsent(r.forDomain, r);
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} else {
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catchAll.add(r);
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for (int r = 0; r < RELAY_COUNT; r++) {
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Relay relay = new Relay();
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// Use deterministic msgids: relay*1000 + task index
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for (int t = 0; t < TASK_COUNT; t++) {
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relay.addTask((long)(r * 1000 + t));
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}
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relays.add(relay);
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}
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long ops = 0;
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for (Envelope evp : envelopes) {
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ops++; // O(1) hash lookup
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Rule candidate = domainIndex.get(evp.destDomain);
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if (candidate != null && candidate.matches(evp.destDomain, evp.srcDomain)) {
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// matched — done
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} else {
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// fallback to catch-all rules (typically 1-2)
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for (Rule r : catchAll) {
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ops++;
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if (r.matches(evp.destDomain, evp.srcDomain)) break;
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// --- LINEAR SCAN simulation ---
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linearComparisons = 0;
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for (int r = 0; r < RELAY_COUNT; r++) {
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Relay relay = relays.get(r);
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for (int e = 0; e < ENVELOPE_COUNT; e++) {
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// Each envelope targets an existing task (worst-case: last task)
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long msgid = (long)(r * 1000 + (TASK_COUNT - 1));
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boolean found = relay.findLinear(msgid);
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if (!found) {
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System.err.println("FAIL: linear search missed existing task");
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System.exit(1);
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}
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}
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}
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return ops;
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}
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long linearTotal = linearComparisons;
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// ── bench harness ─────────────────────────────────────────────────────────
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// --- HASH LOOKUP simulation ---
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hashLookups = 0;
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for (int r = 0; r < RELAY_COUNT; r++) {
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Relay relay = relays.get(r);
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for (int e = 0; e < ENVELOPE_COUNT; e++) {
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long msgid = (long)(r * 1000 + (TASK_COUNT - 1));
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boolean found = relay.findHash(msgid);
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if (!found) {
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System.err.println("FAIL: hash lookup missed existing task");
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System.exit(1);
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}
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}
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}
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long hashTotal = hashLookups;
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static void bench(String label, Runnable slow, Runnable fast, long sOps, long fOps) {
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slow.run(); fast.run();
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long t0 = System.nanoTime(); slow.run(); long sMs = (System.nanoTime() - t0) / 1_000_000;
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long t1 = System.nanoTime(); fast.run(); long fMs = (System.nanoTime() - t1) / 1_000_000;
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double r = fOps > 0 ? (double) sOps / fOps : 0;
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System.out.printf(" %-56s slow:%4dms (%,d ops) fast:%4dms (%,d ops) speedup:%.0fx%n",
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label, sMs, sOps, fMs, fOps, r);
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}
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double ratio = (double) linearTotal / (double) hashTotal;
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// ── main ──────────────────────────────────────────────────────────────────
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System.out.println("opensmtpd-0001: mta_handle_envelope task-lookup benchmark");
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System.out.println(" relays : " + RELAY_COUNT);
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System.out.println(" tasks/relay : " + TASK_COUNT);
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System.out.println(" envelopes : " + ENVELOPE_COUNT + " per relay");
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System.out.println(" linear ops : " + linearTotal
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+ " (TAILQ_FOREACH scan)");
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System.out.println(" hash ops : " + hashTotal
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+ " (tree_get / HashMap)");
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System.out.printf (" ratio : %.1fx%n", ratio);
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System.out.println(" threshold : " + RATIO_THRESHOLD + "x");
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public static void main(String[] args) {
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final int R = 300; // policy rules in smtpd.conf
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final int M = 2000; // recipient envelopes per message burst
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if (ratio < RATIO_THRESHOLD) {
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System.err.printf("FAIL: ratio %.1f < threshold %d%n",
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ratio, RATIO_THRESHOLD);
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System.exit(1);
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}
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List<Rule> rules = buildRules(R);
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// Worst-case scenario: envelopes are spread across all R domains,
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// so the average rule scan depth is R/2. With R=300 rules and M=2000
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// envelopes, the TAILQ scan does O(R/2 × M) = 300,000 evaluations.
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// The hash dispatch does O(1) per envelope = M evaluations.
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List<Envelope> envelopes = new ArrayList<>(M);
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for (int i = 0; i < M; i++)
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envelopes.add(new Envelope(
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"dest-" + (i % R) + ".example.com", // uniformly distributed across all rules
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"sender.example.com"));
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System.out.println("OpensmtpdTest — CWE-407");
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System.out.println();
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System.out.println("opensmtpd-0001: ruleset_match() TAILQ scan");
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final long[] sOps = new long[1], fOps = new long[1];
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bench(String.format("ruleset_match R=%d rules, M=%d envelopes", R, M),
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() -> { sOps[0] = rulesetMatchSlow(rules, envelopes); },
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() -> { fOps[0] = rulesetMatchFast(rules, envelopes); },
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rulesetMatchSlow(rules, envelopes),
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rulesetMatchFast(rules, envelopes));
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assert sOps[0] > fOps[0] * 10 :
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"opensmtpd-0001: expected >10x more ops slow vs fast, got slow="
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+ sOps[0] + " fast=" + fOps[0];
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System.out.println();
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System.out.println("All assertions passed.");
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System.out.println("ALL PASS");
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}
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}
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