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https://github.com/cesanta/mongoose.git
synced 2026-10-23 11:44:53 +00:00
Fix TCP error handling
Add unit tests for TCP error handling Account for options in TCP header for payload start address calculation Take UDP payload length from UDP header
This commit is contained in:
Sergio R. Caprile committed
1 parent
c1152f5eeb
commit
7339c7dfe7
3 files changed
+472
-139
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+66
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@@ -572,13 +572,17 @@ static size_t tx_tcp(struct mg_tcpip_if *ifp, uint8_t *dst_mac, uint32_t dst_ip,
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return ether_output(ifp, PDIFF(ifp->tx.buf, tcp + 1) + len);
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}
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static size_t tx_tcp_pkt(struct mg_tcpip_if *ifp, struct pkt *pkt,
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uint8_t flags, uint32_t seq, const void *buf,
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size_t len) {
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uint32_t delta = (pkt->tcp->flags & (TH_SYN | TH_FIN)) ? 1 : 0;
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static size_t tx_tcp_ctrlresp(struct mg_tcpip_if *ifp, struct pkt *pkt,
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uint8_t flags, uint32_t seqno) {
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uint32_t ackno = mg_htonl(mg_ntohl(pkt->tcp->seq) + (uint32_t) pkt->pay.len +
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((pkt->tcp->flags & (TH_SYN | TH_FIN)) ? 1 : 0));
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return tx_tcp(ifp, pkt->eth->src, pkt->ip->src, flags, pkt->tcp->dport,
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pkt->tcp->sport, seq, mg_htonl(mg_ntohl(pkt->tcp->seq) + delta),
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buf, len);
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pkt->tcp->sport, seqno, ackno, NULL, 0);
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}
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static size_t tx_tcp_rst(struct mg_tcpip_if *ifp, struct pkt *pkt, bool toack) {
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return tx_tcp_ctrlresp(ifp, pkt, toack ? TH_RST : (TH_RST | TH_ACK),
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toack ? pkt->tcp->ack : 0);
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}
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static struct mg_connection *accept_conn(struct mg_connection *lsn,
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@@ -777,10 +781,9 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
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}
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}
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// TCP backlog
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struct mg_backlog {
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uint16_t port, mss; // use port=0 for available entries
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uint16_t port, mss; // use port=0 for available entries
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uint8_t age;
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};
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@@ -790,7 +793,7 @@ static int backlog_insert(struct mg_connection *c, uint16_t port,
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size_t i;
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for (i = 0; i < sizeof(c->data) / sizeof(*p); i++) {
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if (p[i].port != 0) continue;
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p[i].age = 2; // remove after two calls, average 1.5 call rate
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p[i].age = 2; // remove after two calls, average 1.5 call rate
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p[i].port = port, p[i].mss = mss;
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return (int) i;
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}
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@@ -813,7 +816,7 @@ static void backlog_remove(struct mg_connection *c, uint16_t key) {
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static void backlog_maintain(struct mg_connection *c) {
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struct mg_backlog *p = (struct mg_backlog *) c->data;
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size_t i; // dec age and remove those where it reaches 0
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size_t i; // dec age and remove those where it reaches 0
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for (i = 0; i < sizeof(c->data) / sizeof(*p); i++) {
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if (p[i].port == 0) continue;
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if (p[i].age != 0) --p[i].age;
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@@ -850,70 +853,74 @@ static void handle_opt(struct connstate *s, struct tcp *tcp) {
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static void rx_tcp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
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struct mg_connection *c = getpeer(ifp->mgr, pkt, false);
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struct connstate *s = c == NULL ? NULL : (struct connstate *) (c + 1);
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#if 0
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MG_INFO(("%lu %hhu %d", c ? c->id : 0, pkt->tcp->flags, (int) pkt->pay.len));
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#endif
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// Order is VERY important; RFC-9293 3.5.2
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// - check clients (Group 1) and established connections (Group 3)
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if (c != NULL && c->is_connecting && pkt->tcp->flags == (TH_SYN | TH_ACK)) {
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// client got a server connection accept
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handle_opt(s, pkt->tcp); // process options (MSS)
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s->seq = mg_ntohl(pkt->tcp->ack), s->ack = mg_ntohl(pkt->tcp->seq) + 1;
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tx_tcp_pkt(ifp, pkt, TH_ACK, pkt->tcp->ack, NULL, 0);
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tx_tcp_ctrlresp(ifp, pkt, TH_ACK, pkt->tcp->ack);
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c->is_connecting = 0; // Client connected
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settmout(c, MIP_TTYPE_KEEPALIVE);
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mg_call(c, MG_EV_CONNECT, NULL); // Let user know
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if (c->is_tls_hs) mg_tls_handshake(c);
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if (!c->is_tls_hs) c->is_tls = 0; // user did not call mg_tls_init()
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} else if (c != NULL && c->is_connecting && pkt->tcp->flags != TH_ACK) {
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// mg_hexdump(pkt->raw.buf, pkt->raw.len);
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tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
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mg_error(c, "connection refused");
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} else if (c != NULL && pkt->tcp->flags & TH_RST) {
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// TODO(): validate RST is within window (and optional with proper ACK)
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mg_error(c, "peer RST"); // RFC-1122 4.2.2.13
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} else if (c != NULL) {
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#if 0
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MG_DEBUG(("%lu %d %M:%hu -> %M:%hu", c->id, (int) pkt->raw.len,
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mg_print_ip4, &pkt->ip->src, mg_ntohs(pkt->tcp->sport),
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mg_print_ip4, &pkt->ip->dst, mg_ntohs(pkt->tcp->dport)));
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mg_hexdump(pkt->pay.buf, pkt->pay.len);
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#endif
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// process segment
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s->tmiss = 0; // Reset missed keep-alive counter
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if (s->ttype == MIP_TTYPE_KEEPALIVE) // Advance keep-alive timer
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settmout(c,
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MIP_TTYPE_KEEPALIVE); // unless a former ACK timeout is pending
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read_conn(c, pkt); // Override timer with ACK timeout if needed
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} else if ((c = getpeer(ifp->mgr, pkt, true)) == NULL) {
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tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
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} else if (pkt->tcp->flags & TH_RST) {
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if (c->is_accepted) mg_error(c, "peer RST"); // RFC-1122 4.2.2.13
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// ignore RST if not connected
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} else if (pkt->tcp->flags & TH_SYN) {
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struct connstate cs; // At this point, s = NULL, there is no connection
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int key;
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uint32_t isn;
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if (pkt->tcp->sport != 0) {
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handle_opt(&cs, pkt->tcp); // process options (MSS)
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key = backlog_insert(c, pkt->tcp->sport, cs.dmss); // backlog options (MSS)
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if (key < 0) return; // no room in backlog, discard SYN, client retries
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// Use peer's src port and bl key as ISN, to later identify the handshake
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isn = (mg_htonl(((uint32_t)key << 16) | mg_ntohs(pkt->tcp->sport)));
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tx_tcp_pkt(ifp, pkt, TH_SYN | TH_ACK, isn, NULL, 0);
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} // what should we do when port=0 ? Linux takes port 0 as any other port
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} else if (pkt->tcp->flags & TH_FIN) {
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tx_tcp_pkt(ifp, pkt, TH_FIN | TH_ACK, pkt->tcp->ack, NULL, 0);
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} else if ((uint16_t) (mg_htonl(pkt->tcp->ack) - 1) ==
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mg_htons(pkt->tcp->sport)) {
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uint16_t key = (uint16_t) ((mg_htonl(pkt->tcp->ack) - 1) >> 16);
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struct mg_backlog *b = backlog_retrieve(c, key, pkt->tcp->sport);
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if (b != NULL) {
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accept_conn(c, pkt, b->mss); // pass options
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backlog_remove(c, key);
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} else if (!c->is_accepted) { // not an actual match, reset
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tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
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// TODO(scaprile): revisit this and below, weird scenarios
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}
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} else if (!c->is_accepted) { // no peer
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tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
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} else {
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// MG_VERBOSE(("dropped silently.."));
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}
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} else
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// - we don't listen on that port; RFC-9293 3.5.2 Group 1
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// - check listening connections; RFC-9293 3.5.2 Group 2
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if ((c = getpeer(ifp->mgr, pkt, true)) == NULL) {
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// not listening on that port
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if (!(pkt->tcp->flags & TH_RST)) {
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tx_tcp_rst(ifp, pkt, pkt->tcp->flags & TH_ACK);
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} // else silently discard
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} else if (pkt->tcp->flags == TH_SYN) {
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// listener receives a connection request
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struct connstate cs; // At this point, s = NULL, there is no connection
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int key;
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uint32_t isn;
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if (pkt->tcp->sport != 0) {
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handle_opt(&cs, pkt->tcp); // process options (MSS)
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key = backlog_insert(c, pkt->tcp->sport,
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cs.dmss); // backlog options (MSS)
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if (key < 0) return; // no room in backlog, discard SYN, client retries
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// Use peer's src port and bl key as ISN, to later identify the
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// handshake
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isn = (mg_htonl(((uint32_t) key << 16) | mg_ntohs(pkt->tcp->sport)));
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tx_tcp_ctrlresp(ifp, pkt, TH_SYN | TH_ACK, isn);
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} // what should we do when port=0 ? Linux takes port 0 as any other
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// port
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} else if (pkt->tcp->flags == TH_ACK) {
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// listener receives an ACK
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struct mg_backlog *b = NULL;
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if ((uint16_t) (mg_htonl(pkt->tcp->ack) - 1) ==
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mg_htons(pkt->tcp->sport)) {
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uint16_t key = (uint16_t) ((mg_htonl(pkt->tcp->ack) - 1) >> 16);
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b = backlog_retrieve(c, key, pkt->tcp->sport);
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if (b != NULL) { // ACK is a response to a SYN+ACK
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accept_conn(c, pkt, b->mss); // pass options
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backlog_remove(c, key);
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} // else not an actual match, reset
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}
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if (b == NULL) tx_tcp_rst(ifp, pkt, true);
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} else if (pkt->tcp->flags & TH_RST) {
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// silently discard
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} else if (pkt->tcp->flags & TH_ACK) { // ACK + something else != RST
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tx_tcp_rst(ifp, pkt, true);
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} else if (pkt->tcp->flags & TH_SYN) { // SYN + something else != ACK
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tx_tcp_rst(ifp, pkt, false);
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} // else silently discard
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}
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static void rx_ip(struct mg_tcpip_if *ifp, struct pkt *pkt) {
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@@ -933,6 +940,7 @@ static void rx_ip(struct mg_tcpip_if *ifp, struct pkt *pkt) {
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pkt->udp = (struct udp *) (pkt->ip + 1);
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if (pkt->pay.len < sizeof(*pkt->udp)) return;
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mkpay(pkt, pkt->udp + 1);
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if (pkt->udp->len < pkt->pay.len) pkt->pay.len = pkt->udp->len;
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MG_VERBOSE(("UDP %M:%hu -> %M:%hu len %u", mg_print_ip4, &pkt->ip->src,
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mg_ntohs(pkt->udp->sport), mg_print_ip4, &pkt->ip->dst,
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mg_ntohs(pkt->udp->dport), (int) pkt->pay.len));
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@@ -951,7 +959,7 @@ static void rx_ip(struct mg_tcpip_if *ifp, struct pkt *pkt) {
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uint16_t iplen, off;
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pkt->tcp = (struct tcp *) (pkt->ip + 1);
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if (pkt->pay.len < sizeof(*pkt->tcp)) return;
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mkpay(pkt, pkt->tcp + 1);
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mkpay(pkt, (uint32_t *) pkt->tcp + (pkt->tcp->off >> 4)); // may have opts
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iplen = mg_ntohs(pkt->ip->len);
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off = (uint16_t) (sizeof(*pkt->ip) + ((pkt->tcp->off >> 4) * 4U));
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if (iplen >= off) pkt->pay.len = (size_t) (iplen - off);
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