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Implement ARP resolution for local LANs
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@cpq
cpq committed Aug 3, 2023
1 parent 2db41ae commit 697576b
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Showing 2 changed files with 90 additions and 56 deletions.
73 changes: 45 additions & 28 deletions mongoose.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7733,6 +7733,7 @@ struct mg_tcpip_driver mg_tcpip_driver_w5500 = {w5500_init, w5500_tx, w5500_rx,
#endif

#define MIP_TCP_ACK_MS 150 // Timeout for ACKing
#define MIP_TCP_ARP_MS 100 // Timeout for ARP response

struct connstate {
uint32_t seq, ack; // TCP seq/ack counters
Expand All @@ -7741,6 +7742,7 @@ struct connstate {
uint8_t ttype; // Timer type. 0: ack, 1: keep-alive
#define MIP_TTYPE_KEEPALIVE 0 // Connection is idle for long, send keepalive
#define MIP_TTYPE_ACK 1 // Peer sent us data, we have to ack it soon
#define MIP_TTYPE_ARP 2 // ARP resolve sent, waiting for response
uint8_t tmiss; // Number of keep-alive misses
struct mg_iobuf raw; // For TLS only. Incoming raw data
};
Expand Down Expand Up @@ -7851,6 +7853,8 @@ struct pkt {
struct dhcp *dhcp;
};

static void send_syn(struct mg_connection *c);

static void mkpay(struct pkt *pkt, void *p) {
pkt->pay =
mg_str_n((char *) p, (size_t) (&pkt->raw.ptr[pkt->raw.len] - (char *) p));
Expand All @@ -7872,6 +7876,17 @@ static uint16_t ipcsum(const void *buf, size_t len) {
return csumfin(sum);
}

static void settmout(struct mg_connection *c, uint8_t type) {
struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->mgr->priv;
struct connstate *s = (struct connstate *) (c + 1);
unsigned n = type == MIP_TTYPE_ACK ? MIP_TCP_ACK_MS
: type == MIP_TTYPE_ARP ? MIP_TCP_ARP_MS
: MIP_TCP_KEEPALIVE_MS;
s->timer = ifp->now + n;
s->ttype = type;
MG_VERBOSE(("%lu %d -> %llx", c->id, type, s->timer));
}

static size_t ether_output(struct mg_tcpip_if *ifp, size_t len) {
// size_t min = 64; // Pad short frames to 64 bytes (minimum Ethernet size)
// if (len < min) memset(ifp->tx.ptr + len, 0, min - len), len = min;
Expand Down Expand Up @@ -8009,6 +8024,9 @@ static struct mg_connection *getpeer(struct mg_mgr *mgr, struct pkt *pkt,
bool lsn) {
struct mg_connection *c = NULL;
for (c = mgr->conns; c != NULL; c = c->next) {
if (c->is_arplooking && pkt->arp &&
memcmp(&pkt->arp->spa, c->rem.ip, sizeof(pkt->arp->spa)) == 0)
break;
if (c->is_udp && pkt->udp && c->loc.port == pkt->udp->dport) break;
if (!c->is_udp && pkt->tcp && c->loc.port == pkt->tcp->dport &&
lsn == c->is_listening && (lsn || c->rem.port == pkt->tcp->sport))
Expand All @@ -8033,8 +8051,8 @@ static void rx_arp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
memcpy(arp->sha, ifp->mac, sizeof(pkt->arp->sha));
arp->tpa = pkt->arp->spa;
arp->spa = ifp->ip;
MG_DEBUG(("ARP: tell %M we're %M", mg_print_ip4, &arp->tpa, mg_print_ip4,
&ifp->ip));
MG_DEBUG(("ARP: tell %M we're %M", mg_print_ip4, &arp->tpa, mg_print_mac,
&ifp->mac));
ether_output(ifp, PDIFF(eth, arp + 1));
} else if (pkt->arp->op == mg_htons(2)) {
if (memcmp(pkt->arp->tha, ifp->mac, sizeof(pkt->arp->tha)) != 0) return;
Expand All @@ -8049,6 +8067,8 @@ static void rx_arp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
MG_DEBUG(("%lu ARP resolved %M -> %M", c->id, mg_print_ip4, c->rem.ip,
mg_print_mac, s->mac));
c->is_arplooking = 0;
settmout(c, MIP_TTYPE_KEEPALIVE);
send_syn(c);
}
}
}
Expand Down Expand Up @@ -8200,9 +8220,10 @@ static size_t tx_tcp(struct mg_tcpip_if *ifp, uint8_t *dst_mac, uint32_t dst_ip,
cs = csumup(cs, &ip->dst, sizeof(ip->dst));
cs = csumup(cs, pseudo, sizeof(pseudo));
tcp->csum = csumfin(cs);
MG_DEBUG(("TCP %M:%hu -> %M:%hu fl %x len %u", mg_print_ip4, &ip->src,
mg_ntohs(tcp->sport), mg_print_ip4, &ip->dst, mg_ntohs(tcp->dport),
tcp->flags, (int) len));
MG_VERBOSE(("TCP %M:%hu -> %M:%hu fl %x len %u", mg_print_ip4, &ip->src,
mg_ntohs(tcp->sport), mg_print_ip4, &ip->dst,
mg_ntohs(tcp->dport), tcp->flags, (int) len));
// mg_hexdump(ifp->tx.ptr, PDIFF(ifp->tx.ptr, tcp + 1) + len);
return ether_output(ifp, PDIFF(ifp->tx.ptr, tcp + 1) + len);
}

Expand All @@ -8215,15 +8236,6 @@ static size_t tx_tcp_pkt(struct mg_tcpip_if *ifp, struct pkt *pkt,
buf, len);
}

static void settmout(struct mg_connection *c, uint8_t type) {
struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->mgr->priv;
struct connstate *s = (struct connstate *) (c + 1);
unsigned n = type == MIP_TTYPE_ACK ? MIP_TCP_ACK_MS : MIP_TCP_KEEPALIVE_MS;
s->timer = ifp->now + n;
s->ttype = type;
MG_VERBOSE(("%lu %d -> %llx", c->id, type, s->timer));
}

static struct mg_connection *accept_conn(struct mg_connection *lsn,
struct pkt *pkt) {
struct mg_connection *c = mg_alloc_conn(lsn->mgr);
Expand Down Expand Up @@ -8284,7 +8296,6 @@ long mg_io_recv(struct mg_connection *c, void *buf, size_t len) {
if (len > s->raw.len) len = s->raw.len;
memcpy(buf, s->raw.buf, len);
mg_iobuf_del(&s->raw, 0, len);
MG_DEBUG(("%lu", len));
return (long) len;
}

Expand All @@ -8305,7 +8316,7 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
} else {
uint32_t rem_ip;
memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));
MG_DEBUG(("SEQ != ACK: %x %x %x", seq, s->ack, ack));
MG_VERBOSE(("SEQ != ACK: %x %x %x", seq, s->ack, ack));
tx_tcp((struct mg_tcpip_if *) c->mgr->priv, s->mac, rem_ip, TH_ACK,
c->loc.port, c->rem.port, mg_htonl(s->seq), mg_htonl(s->ack), "",
0);
Expand All @@ -8322,7 +8333,7 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
memcpy(&io->buf[io->len], pkt->pay.ptr, pkt->pay.len);
io->len += pkt->pay.len;

MG_DEBUG(("%lu SEQ %x -> %x", c->id, mg_htonl(pkt->tcp->seq), s->ack));
MG_VERBOSE(("%lu SEQ %x -> %x", c->id, mg_htonl(pkt->tcp->seq), s->ack));
// Advance ACK counter
s->ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len);
#if 0
Expand Down Expand Up @@ -8375,6 +8386,7 @@ static void rx_tcp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
settmout(c, MIP_TTYPE_KEEPALIVE);
mg_call(c, MG_EV_CONNECT, NULL); // Let user know
} else if (c != NULL && c->is_connecting) {
// mg_hexdump(pkt->raw.ptr, pkt->raw.len);
tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
} else if (c != NULL && pkt->tcp->flags & TH_RST) {
mg_error(c, "peer RST"); // RFC-1122 4.2.2.13
Expand All @@ -8383,7 +8395,7 @@ static void rx_tcp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
MG_DEBUG(("%lu %d %M:%hu -> %M:%hu", c->id, (int) pkt->raw.len,
mg_print_ip4, &pkt->ip->src, mg_ntohs(pkt->tcp->sport),
mg_print_ip4, &pkt->ip->dst, mg_ntohs(pkt->tcp->dport)));
mg_hexdump(pkt->pay.buf, pkt->pay.len);
mg_hexdump(pkt->pay.ptr, pkt->pay.len);
#endif
s->tmiss = 0; // Reset missed keep-alive counter
if (s->ttype == MIP_TTYPE_KEEPALIVE) // Advance keep-alive timer
Expand All @@ -8406,7 +8418,7 @@ static void rx_tcp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
} else if (!c->is_accepted) { // no peer
tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
} else {
// MG_DEBUG(("dropped silently.."));
// MG_VERBOSE(("dropped silently.."));
}
}

Expand All @@ -8420,9 +8432,9 @@ static void rx_ip(struct mg_tcpip_if *ifp, struct pkt *pkt) {
pkt->udp = (struct udp *) (pkt->ip + 1);
if (pkt->pay.len < sizeof(*pkt->udp)) return;
mkpay(pkt, pkt->udp + 1);
MG_DEBUG(("UDP %M:%hu -> %M:%hu len %u", mg_print_ip4, &pkt->ip->src,
mg_ntohs(pkt->udp->sport), mg_print_ip4, &pkt->ip->dst,
mg_ntohs(pkt->udp->dport), (int) pkt->pay.len));
MG_VERBOSE(("UDP %M:%hu -> %M:%hu len %u", mg_print_ip4, &pkt->ip->src,
mg_ntohs(pkt->udp->sport), mg_print_ip4, &pkt->ip->dst,
mg_ntohs(pkt->udp->dport), (int) pkt->pay.len));
if (ifp->enable_dhcp_client && pkt->udp->dport == mg_htons(68)) {
pkt->dhcp = (struct dhcp *) (pkt->udp + 1);
mkpay(pkt, pkt->dhcp + 1);
Expand All @@ -8441,9 +8453,9 @@ static void rx_ip(struct mg_tcpip_if *ifp, struct pkt *pkt) {
uint16_t iplen = mg_ntohs(pkt->ip->len);
uint16_t off = (uint16_t) (sizeof(*pkt->ip) + ((pkt->tcp->off >> 4) * 4U));
if (iplen >= off) pkt->pay.len = (size_t) (iplen - off);
MG_DEBUG(("TCP %M:%hu -> %M:%hu len %u", mg_print_ip4, &pkt->ip->src,
mg_ntohs(pkt->tcp->sport), mg_print_ip4, &pkt->ip->dst,
mg_ntohs(pkt->tcp->dport), (int) pkt->pay.len));
MG_VERBOSE(("TCP %M:%hu -> %M:%hu len %u", mg_print_ip4, &pkt->ip->src,
mg_ntohs(pkt->tcp->sport), mg_print_ip4, &pkt->ip->dst,
mg_ntohs(pkt->tcp->dport), (int) pkt->pay.len));
rx_tcp(ifp, pkt);
}
}
Expand Down Expand Up @@ -8564,14 +8576,16 @@ static void mg_tcpip_poll(struct mg_tcpip_if *ifp, uint64_t uptime_ms) {
memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));
if (uptime_ms > s->timer) {
if (s->ttype == MIP_TTYPE_ACK) {
MG_DEBUG(("%lu ack %x %x", c->id, s->seq, s->ack));
MG_VERBOSE(("%lu ack %x %x", c->id, s->seq, s->ack));
tx_tcp(ifp, s->mac, rem_ip, TH_ACK, c->loc.port, c->rem.port,
mg_htonl(s->seq), mg_htonl(s->ack), "", 0);
} else if (s->ttype == MIP_TTYPE_ARP) {
mg_error(c, "ARP timeout");
} else {
if (s->tmiss++ > 2) {
mg_error(c, "keepalive");
} else {
MG_DEBUG(("%lu keepalive", c->id));
MG_VERBOSE(("%lu keepalive", c->id));
tx_tcp(ifp, s->mac, rem_ip, TH_ACK, c->loc.port, c->rem.port,
mg_htonl(s->seq - 1), mg_htonl(s->ack), "", 0);
}
Expand Down Expand Up @@ -8661,7 +8675,9 @@ void mg_connect_resolved(struct mg_connection *c) {
// If we're in the same LAN, fire an ARP lookup. TODO(cpq): handle this!
MG_DEBUG(("%lu ARP lookup...", c->id));
arp_ask(ifp, rem_ip);
settmout(c, MIP_TTYPE_ARP);
c->is_arplooking = 1;
c->is_connecting = 1;
} else if (rem_ip == (ifp->ip | ~ifp->mask)) {
struct connstate *s = (struct connstate *) (c + 1);
memset(s->mac, 0xFF, sizeof(s->mac)); // local broadcast
Expand Down Expand Up @@ -8702,7 +8718,8 @@ static void close_conn(struct mg_connection *c) {
uint32_t rem_ip;
memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));
mg_iobuf_free(&s->raw); // For TLS connections, release raw data
if (c->is_udp == false && c->is_listening == false) { // For TCP conns,
if (c->is_udp == false && c->is_listening == false &&
c->is_connecting == false) { // For TCP conns,
struct mg_tcpip_if *ifp =
(struct mg_tcpip_if *) c->mgr->priv; // send TCP FIN
tx_tcp(ifp, s->mac, rem_ip, TH_FIN | TH_ACK, c->loc.port, c->rem.port,
Expand Down
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