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net_builtin.c
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net_builtin.c
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#include "net_builtin.h"
#if defined(MG_ENABLE_TCPIP) && MG_ENABLE_TCPIP
#define MG_EPHEMERAL_PORT_BASE 32768
#define PDIFF(a, b) ((size_t) (((char *) (b)) - ((char *) (a))))
#ifndef MIP_TCP_KEEPALIVE_MS
#define MIP_TCP_KEEPALIVE_MS 45000 // TCP keep-alive period, ms
#endif
#define MIP_TCP_ACK_MS 150 // Timeout for ACKing
#define MIP_TCP_ARP_MS 100 // Timeout for ARP response
#define MIP_TCP_SYN_MS 15000 // Timeout for connection establishment
#define MIP_TCP_FIN_MS 1000 // Timeout for closing connection
#define MIP_TCP_WIN 6000 // TCP window size
struct connstate {
uint32_t seq, ack; // TCP seq/ack counters
uint64_t timer; // TCP keep-alive / ACK timer
uint32_t acked; // Last ACK-ed number
size_t unacked; // Not acked bytes
uint8_t mac[6]; // Peer MAC address
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
#define MIP_TTYPE_SYN 3 // SYN sent, waiting for response
#define MIP_TTYPE_FIN 4 // FIN sent, waiting until terminating the connection
uint8_t tmiss; // Number of keep-alive misses
struct mg_iobuf raw; // For TLS only. Incoming raw data
};
#pragma pack(push, 1)
struct lcp {
uint8_t addr, ctrl, proto[2], code, id, len[2];
};
struct eth {
uint8_t dst[6]; // Destination MAC address
uint8_t src[6]; // Source MAC address
uint16_t type; // Ethernet type
};
struct ip {
uint8_t ver; // Version
uint8_t tos; // Unused
uint16_t len; // Length
uint16_t id; // Unused
uint16_t frag; // Fragmentation
#define IP_FRAG_OFFSET_MSK 0xFF1F
#define IP_MORE_FRAGS_MSK 0x20
uint8_t ttl; // Time to live
uint8_t proto; // Upper level protocol
uint16_t csum; // Checksum
uint32_t src; // Source IP
uint32_t dst; // Destination IP
};
struct ip6 {
uint8_t ver; // Version
uint8_t opts[3]; // Options
uint16_t len; // Length
uint8_t proto; // Upper level protocol
uint8_t ttl; // Time to live
uint8_t src[16]; // Source IP
uint8_t dst[16]; // Destination IP
};
struct icmp {
uint8_t type;
uint8_t code;
uint16_t csum;
};
struct arp {
uint16_t fmt; // Format of hardware address
uint16_t pro; // Format of protocol address
uint8_t hlen; // Length of hardware address
uint8_t plen; // Length of protocol address
uint16_t op; // Operation
uint8_t sha[6]; // Sender hardware address
uint32_t spa; // Sender protocol address
uint8_t tha[6]; // Target hardware address
uint32_t tpa; // Target protocol address
};
struct tcp {
uint16_t sport; // Source port
uint16_t dport; // Destination port
uint32_t seq; // Sequence number
uint32_t ack; // Acknowledgement number
uint8_t off; // Data offset
uint8_t flags; // TCP flags
#define TH_FIN 0x01
#define TH_SYN 0x02
#define TH_RST 0x04
#define TH_PUSH 0x08
#define TH_ACK 0x10
#define TH_URG 0x20
#define TH_ECE 0x40
#define TH_CWR 0x80
uint16_t win; // Window
uint16_t csum; // Checksum
uint16_t urp; // Urgent pointer
};
struct udp {
uint16_t sport; // Source port
uint16_t dport; // Destination port
uint16_t len; // UDP length
uint16_t csum; // UDP checksum
};
struct dhcp {
uint8_t op, htype, hlen, hops;
uint32_t xid;
uint16_t secs, flags;
uint32_t ciaddr, yiaddr, siaddr, giaddr;
uint8_t hwaddr[208];
uint32_t magic;
uint8_t options[32];
};
#pragma pack(pop)
struct pkt {
struct mg_str raw; // Raw packet data
struct mg_str pay; // Payload data
struct eth *eth;
struct llc *llc;
struct arp *arp;
struct ip *ip;
struct ip6 *ip6;
struct icmp *icmp;
struct tcp *tcp;
struct udp *udp;
struct dhcp *dhcp;
};
static void mg_tcpip_call(struct mg_tcpip_if *ifp, int ev, void *ev_data) {
if (ifp->fn != NULL) ifp->fn(ifp, ev, ev_data);
}
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.buf[pkt->raw.len] - (char *) p));
}
static uint32_t csumup(uint32_t sum, const void *buf, size_t len) {
size_t i;
const uint8_t *p = (const uint8_t *) buf;
for (i = 0; i < len; i++) sum += i & 1 ? p[i] : (uint32_t) (p[i] << 8);
return sum;
}
static uint16_t csumfin(uint32_t sum) {
while (sum >> 16) sum = (sum & 0xffff) + (sum >> 16);
return mg_htons(~sum & 0xffff);
}
static uint16_t ipcsum(const void *buf, size_t len) {
uint32_t sum = csumup(0, buf, 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
: type == MIP_TTYPE_SYN ? MIP_TCP_SYN_MS
: type == MIP_TTYPE_FIN ? MIP_TCP_FIN_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 n = ifp->driver->tx(ifp->tx.buf, len, ifp);
if (n == len) ifp->nsent++;
return n;
}
static void arp_ask(struct mg_tcpip_if *ifp, uint32_t ip) {
struct eth *eth = (struct eth *) ifp->tx.buf;
struct arp *arp = (struct arp *) (eth + 1);
memset(eth->dst, 255, sizeof(eth->dst));
memcpy(eth->src, ifp->mac, sizeof(eth->src));
eth->type = mg_htons(0x806);
memset(arp, 0, sizeof(*arp));
arp->fmt = mg_htons(1), arp->pro = mg_htons(0x800), arp->hlen = 6,
arp->plen = 4;
arp->op = mg_htons(1), arp->tpa = ip, arp->spa = ifp->ip;
memcpy(arp->sha, ifp->mac, sizeof(arp->sha));
ether_output(ifp, PDIFF(eth, arp + 1));
}
static void onstatechange(struct mg_tcpip_if *ifp) {
if (ifp->state == MG_TCPIP_STATE_READY) {
MG_INFO(("READY, IP: %M", mg_print_ip4, &ifp->ip));
MG_INFO((" GW: %M", mg_print_ip4, &ifp->gw));
MG_INFO((" MAC: %M", mg_print_mac, &ifp->mac));
arp_ask(ifp, ifp->gw); // unsolicited GW ARP request
} else if (ifp->state == MG_TCPIP_STATE_UP) {
MG_ERROR(("Link up"));
srand((unsigned int) mg_millis());
} else if (ifp->state == MG_TCPIP_STATE_DOWN) {
MG_ERROR(("Link down"));
}
mg_tcpip_call(ifp, MG_TCPIP_EV_ST_CHG, &ifp->state);
}
static struct ip *tx_ip(struct mg_tcpip_if *ifp, uint8_t *mac_dst,
uint8_t proto, uint32_t ip_src, uint32_t ip_dst,
size_t plen) {
struct eth *eth = (struct eth *) ifp->tx.buf;
struct ip *ip = (struct ip *) (eth + 1);
memcpy(eth->dst, mac_dst, sizeof(eth->dst));
memcpy(eth->src, ifp->mac, sizeof(eth->src)); // Use our MAC
eth->type = mg_htons(0x800);
memset(ip, 0, sizeof(*ip));
ip->ver = 0x45; // Version 4, header length 5 words
ip->frag = 0x40; // Don't fragment
ip->len = mg_htons((uint16_t) (sizeof(*ip) + plen));
ip->ttl = 64;
ip->proto = proto;
ip->src = ip_src;
ip->dst = ip_dst;
ip->csum = ipcsum(ip, sizeof(*ip));
return ip;
}
static void tx_udp(struct mg_tcpip_if *ifp, uint8_t *mac_dst, uint32_t ip_src,
uint16_t sport, uint32_t ip_dst, uint16_t dport,
const void *buf, size_t len) {
struct ip *ip =
tx_ip(ifp, mac_dst, 17, ip_src, ip_dst, len + sizeof(struct udp));
struct udp *udp = (struct udp *) (ip + 1);
// MG_DEBUG(("UDP XX LEN %d %d", (int) len, (int) ifp->tx.len));
udp->sport = sport;
udp->dport = dport;
udp->len = mg_htons((uint16_t) (sizeof(*udp) + len));
udp->csum = 0;
uint32_t cs = csumup(0, udp, sizeof(*udp));
cs = csumup(cs, buf, len);
cs = csumup(cs, &ip->src, sizeof(ip->src));
cs = csumup(cs, &ip->dst, sizeof(ip->dst));
cs += (uint32_t) (ip->proto + sizeof(*udp) + len);
udp->csum = csumfin(cs);
memmove(udp + 1, buf, len);
// MG_DEBUG(("UDP LEN %d %d", (int) len, (int) ifp->frame_len));
ether_output(ifp, sizeof(struct eth) + sizeof(*ip) + sizeof(*udp) + len);
}
static void tx_dhcp(struct mg_tcpip_if *ifp, uint8_t *mac_dst, uint32_t ip_src,
uint32_t ip_dst, uint8_t *opts, size_t optslen,
bool ciaddr) {
// https://datatracker.ietf.org/doc/html/rfc2132#section-9.6
struct dhcp dhcp = {1, 1, 6, 0, 0, 0, 0, 0, 0, 0, 0, {0}, 0, {0}};
dhcp.magic = mg_htonl(0x63825363);
memcpy(&dhcp.hwaddr, ifp->mac, sizeof(ifp->mac));
memcpy(&dhcp.xid, ifp->mac + 2, sizeof(dhcp.xid));
memcpy(&dhcp.options, opts, optslen);
if (ciaddr) dhcp.ciaddr = ip_src;
tx_udp(ifp, mac_dst, ip_src, mg_htons(68), ip_dst, mg_htons(67), &dhcp,
sizeof(dhcp));
}
static const uint8_t broadcast[] = {255, 255, 255, 255, 255, 255};
// RFC-2131 #4.3.6, #4.4.1; RFC-2132 #9.8
static void tx_dhcp_request_sel(struct mg_tcpip_if *ifp, uint32_t ip_req,
uint32_t ip_srv) {
uint8_t opts[] = {
53, 1, 3, // Type: DHCP request
12, 3, 'm', 'i', 'p', // Host name: "mip"
54, 4, 0, 0, 0, 0, // DHCP server ID
50, 4, 0, 0, 0, 0, // Requested IP
55, 2, 1, 3, 255, 255, // GW, mask [DNS] [SNTP]
255 // End of options
};
uint8_t addopts = 0;
memcpy(opts + 10, &ip_srv, sizeof(ip_srv));
memcpy(opts + 16, &ip_req, sizeof(ip_req));
if (ifp->enable_req_dns) opts[24 + addopts++] = 6; // DNS
if (ifp->enable_req_sntp) opts[24 + addopts++] = 42; // SNTP
opts[21] += addopts;
tx_dhcp(ifp, (uint8_t *) broadcast, 0, 0xffffffff, opts,
sizeof(opts) + addopts - 2, false);
MG_DEBUG(("DHCP req sent"));
}
// RFC-2131 #4.3.6, #4.4.5 (renewing: unicast, rebinding: bcast)
static void tx_dhcp_request_re(struct mg_tcpip_if *ifp, uint8_t *mac_dst,
uint32_t ip_src, uint32_t ip_dst) {
uint8_t opts[] = {
53, 1, 3, // Type: DHCP request
255 // End of options
};
tx_dhcp(ifp, mac_dst, ip_src, ip_dst, opts, sizeof(opts), true);
MG_DEBUG(("DHCP req sent"));
}
static void tx_dhcp_discover(struct mg_tcpip_if *ifp) {
uint8_t opts[] = {
53, 1, 1, // Type: DHCP discover
55, 2, 1, 3, // Parameters: ip, mask
255 // End of options
};
tx_dhcp(ifp, (uint8_t *) broadcast, 0, 0xffffffff, opts, sizeof(opts), false);
MG_DEBUG(("DHCP discover sent. Our MAC: %M", mg_print_mac, ifp->mac));
}
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))
break;
}
return c;
}
static void rx_arp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
if (pkt->arp->op == mg_htons(1) && pkt->arp->tpa == ifp->ip) {
// ARP request. Make a response, then send
// MG_DEBUG(("ARP op %d %M: %M", mg_ntohs(pkt->arp->op), mg_print_ip4,
// &pkt->arp->spa, mg_print_ip4, &pkt->arp->tpa));
struct eth *eth = (struct eth *) ifp->tx.buf;
struct arp *arp = (struct arp *) (eth + 1);
memcpy(eth->dst, pkt->eth->src, sizeof(eth->dst));
memcpy(eth->src, ifp->mac, sizeof(eth->src));
eth->type = mg_htons(0x806);
*arp = *pkt->arp;
arp->op = mg_htons(2);
memcpy(arp->tha, pkt->arp->sha, sizeof(pkt->arp->tha));
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_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;
if (pkt->arp->spa == ifp->gw) {
// Got response for the GW ARP request. Set ifp->gwmac
memcpy(ifp->gwmac, pkt->arp->sha, sizeof(ifp->gwmac));
} else {
struct mg_connection *c = getpeer(ifp->mgr, pkt, false);
if (c != NULL && c->is_arplooking) {
struct connstate *s = (struct connstate *) (c + 1);
memcpy(s->mac, pkt->arp->sha, sizeof(s->mac));
MG_DEBUG(("%lu ARP resolved %M -> %M", c->id, mg_print_ip4, c->rem.ip,
mg_print_mac, s->mac));
c->is_arplooking = 0;
send_syn(c);
settmout(c, MIP_TTYPE_SYN);
}
}
}
}
static void rx_icmp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
// MG_DEBUG(("ICMP %d", (int) len));
if (pkt->icmp->type == 8 && pkt->ip != NULL && pkt->ip->dst == ifp->ip) {
size_t hlen = sizeof(struct eth) + sizeof(struct ip) + sizeof(struct icmp);
size_t space = ifp->tx.len - hlen, plen = pkt->pay.len;
if (plen > space) plen = space;
struct ip *ip = tx_ip(ifp, pkt->eth->src, 1, ifp->ip, pkt->ip->src,
sizeof(struct icmp) + plen);
struct icmp *icmp = (struct icmp *) (ip + 1);
memset(icmp, 0, sizeof(*icmp)); // Set csum to 0
memcpy(icmp + 1, pkt->pay.buf, plen); // Copy RX payload to TX
icmp->csum = ipcsum(icmp, sizeof(*icmp) + plen);
ether_output(ifp, hlen + plen);
}
}
static void rx_dhcp_client(struct mg_tcpip_if *ifp, struct pkt *pkt) {
uint32_t ip = 0, gw = 0, mask = 0, lease = 0, dns = 0, sntp = 0;
uint8_t msgtype = 0, state = ifp->state;
// perform size check first, then access fields
uint8_t *p = pkt->dhcp->options,
*end = (uint8_t *) &pkt->raw.buf[pkt->raw.len];
if (end < (uint8_t *) (pkt->dhcp + 1)) return;
if (memcmp(&pkt->dhcp->xid, ifp->mac + 2, sizeof(pkt->dhcp->xid))) return;
while (p + 1 < end && p[0] != 255) { // Parse options RFC-1533 #9
if (p[0] == 1 && p[1] == sizeof(ifp->mask) && p + 6 < end) { // Mask
memcpy(&mask, p + 2, sizeof(mask));
} else if (p[0] == 3 && p[1] == sizeof(ifp->gw) && p + 6 < end) { // GW
memcpy(&gw, p + 2, sizeof(gw));
ip = pkt->dhcp->yiaddr;
} else if (ifp->enable_req_dns && p[0] == 6 && p[1] == sizeof(dns) &&
p + 6 < end) { // DNS
memcpy(&dns, p + 2, sizeof(dns));
} else if (ifp->enable_req_sntp && p[0] == 42 && p[1] == sizeof(sntp) &&
p + 6 < end) { // SNTP
memcpy(&sntp, p + 2, sizeof(sntp));
} else if (p[0] == 51 && p[1] == 4 && p + 6 < end) { // Lease
memcpy(&lease, p + 2, sizeof(lease));
lease = mg_ntohl(lease);
} else if (p[0] == 53 && p[1] == 1 && p + 6 < end) { // Msg Type
msgtype = p[2];
}
p += p[1] + 2;
}
// Process message type, RFC-1533 (9.4); RFC-2131 (3.1, 4)
if (msgtype == 6 && ifp->ip == ip) { // DHCPNACK, release IP
ifp->state = MG_TCPIP_STATE_UP, ifp->ip = 0;
} else if (msgtype == 2 && ifp->state == MG_TCPIP_STATE_UP && ip && gw &&
lease) { // DHCPOFFER
// select IP, (4.4.1) (fallback to IP source addr on foul play)
tx_dhcp_request_sel(ifp, ip,
pkt->dhcp->siaddr ? pkt->dhcp->siaddr : pkt->ip->src);
ifp->state = MG_TCPIP_STATE_REQ; // REQUESTING state
} else if (msgtype == 5) { // DHCPACK
if (ifp->state == MG_TCPIP_STATE_REQ && ip && gw && lease) { // got an IP
ifp->lease_expire = ifp->now + lease * 1000;
MG_INFO(("Lease: %u sec (%lld)", lease, ifp->lease_expire / 1000));
// assume DHCP server = router until ARP resolves
memcpy(ifp->gwmac, pkt->eth->src, sizeof(ifp->gwmac));
ifp->ip = ip, ifp->gw = gw, ifp->mask = mask;
ifp->state = MG_TCPIP_STATE_READY; // BOUND state
uint64_t rand;
mg_random(&rand, sizeof(rand));
srand((unsigned int) (rand + mg_millis()));
if (ifp->enable_req_dns && dns != 0)
mg_tcpip_call(ifp, MG_TCPIP_EV_DHCP_DNS, &dns);
if (ifp->enable_req_sntp && sntp != 0)
mg_tcpip_call(ifp, MG_TCPIP_EV_DHCP_SNTP, &sntp);
} else if (ifp->state == MG_TCPIP_STATE_READY && ifp->ip == ip) { // renew
ifp->lease_expire = ifp->now + lease * 1000;
MG_INFO(("Lease: %u sec (%lld)", lease, ifp->lease_expire / 1000));
} // TODO(): accept provided T1/T2 and store server IP for renewal (4.4)
}
if (ifp->state != state) onstatechange(ifp);
}
// Simple DHCP server that assigns a next IP address: ifp->ip + 1
static void rx_dhcp_server(struct mg_tcpip_if *ifp, struct pkt *pkt) {
uint8_t op = 0, *p = pkt->dhcp->options,
*end = (uint8_t *) &pkt->raw.buf[pkt->raw.len];
if (end < (uint8_t *) (pkt->dhcp + 1)) return;
// struct dhcp *req = pkt->dhcp;
struct dhcp res = {2, 1, 6, 0, 0, 0, 0, 0, 0, 0, 0, {0}, 0, {0}};
res.yiaddr = ifp->ip;
((uint8_t *) (&res.yiaddr))[3]++; // Offer our IP + 1
while (p + 1 < end && p[0] != 255) { // Parse options
if (p[0] == 53 && p[1] == 1 && p + 2 < end) { // Message type
op = p[2];
}
p += p[1] + 2;
}
if (op == 1 || op == 3) { // DHCP Discover or DHCP Request
uint8_t msg = op == 1 ? 2 : 5; // Message type: DHCP OFFER or DHCP ACK
uint8_t opts[] = {
53, 1, msg, // Message type
1, 4, 0, 0, 0, 0, // Subnet mask
54, 4, 0, 0, 0, 0, // Server ID
12, 3, 'm', 'i', 'p', // Host name: "mip"
51, 4, 255, 255, 255, 255, // Lease time
255 // End of options
};
memcpy(&res.hwaddr, pkt->dhcp->hwaddr, 6);
memcpy(opts + 5, &ifp->mask, sizeof(ifp->mask));
memcpy(opts + 11, &ifp->ip, sizeof(ifp->ip));
memcpy(&res.options, opts, sizeof(opts));
res.magic = pkt->dhcp->magic;
res.xid = pkt->dhcp->xid;
if (ifp->enable_get_gateway) {
ifp->gw = res.yiaddr;
memcpy(ifp->gwmac, pkt->eth->src, sizeof(ifp->gwmac));
}
tx_udp(ifp, pkt->eth->src, ifp->ip, mg_htons(67),
op == 1 ? ~0U : res.yiaddr, mg_htons(68), &res, sizeof(res));
}
}
static void rx_udp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
struct mg_connection *c = getpeer(ifp->mgr, pkt, true);
if (c == NULL) {
// No UDP listener on this port. Should send ICMP, but keep silent.
} else {
c->rem.port = pkt->udp->sport;
memcpy(c->rem.ip, &pkt->ip->src, sizeof(uint32_t));
struct connstate *s = (struct connstate *) (c + 1);
memcpy(s->mac, pkt->eth->src, sizeof(s->mac));
if (c->recv.len >= MG_MAX_RECV_SIZE) {
mg_error(c, "max_recv_buf_size reached");
} else if (c->recv.size - c->recv.len < pkt->pay.len &&
!mg_iobuf_resize(&c->recv, c->recv.len + pkt->pay.len)) {
mg_error(c, "oom");
} else {
memcpy(&c->recv.buf[c->recv.len], pkt->pay.buf, pkt->pay.len);
c->recv.len += pkt->pay.len;
mg_call(c, MG_EV_READ, &pkt->pay.len);
}
}
}
static size_t tx_tcp(struct mg_tcpip_if *ifp, uint8_t *dst_mac, uint32_t dst_ip,
uint8_t flags, uint16_t sport, uint16_t dport,
uint32_t seq, uint32_t ack, const void *buf, size_t len) {
#if 0
uint8_t opts[] = {2, 4, 5, 0xb4, 4, 2, 0, 0}; // MSS = 1460, SACK permitted
if (flags & TH_SYN) {
// Handshake? Set MSS
buf = opts;
len = sizeof(opts);
}
#endif
struct ip *ip =
tx_ip(ifp, dst_mac, 6, ifp->ip, dst_ip, sizeof(struct tcp) + len);
struct tcp *tcp = (struct tcp *) (ip + 1);
memset(tcp, 0, sizeof(*tcp));
if (buf != NULL && len) memmove(tcp + 1, buf, len);
tcp->sport = sport;
tcp->dport = dport;
tcp->seq = seq;
tcp->ack = ack;
tcp->flags = flags;
tcp->win = mg_htons(MIP_TCP_WIN);
tcp->off = (uint8_t) (sizeof(*tcp) / 4 << 4);
// if (flags & TH_SYN) tcp->off = 0x70; // Handshake? header size 28 bytes
uint32_t cs = 0;
uint16_t n = (uint16_t) (sizeof(*tcp) + len);
uint8_t pseudo[] = {0, ip->proto, (uint8_t) (n >> 8), (uint8_t) (n & 255)};
cs = csumup(cs, tcp, n);
cs = csumup(cs, &ip->src, sizeof(ip->src));
cs = csumup(cs, &ip->dst, sizeof(ip->dst));
cs = csumup(cs, pseudo, sizeof(pseudo));
tcp->csum = csumfin(cs);
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, len));
// mg_hexdump(ifp->tx.buf, PDIFF(ifp->tx.buf, tcp + 1) + len);
return ether_output(ifp, PDIFF(ifp->tx.buf, tcp + 1) + len);
}
static size_t tx_tcp_pkt(struct mg_tcpip_if *ifp, struct pkt *pkt,
uint8_t flags, uint32_t seq, const void *buf,
size_t len) {
uint32_t delta = (pkt->tcp->flags & (TH_SYN | TH_FIN)) ? 1 : 0;
return tx_tcp(ifp, pkt->eth->src, pkt->ip->src, flags, pkt->tcp->dport,
pkt->tcp->sport, seq, mg_htonl(mg_ntohl(pkt->tcp->seq) + delta),
buf, len);
}
static struct mg_connection *accept_conn(struct mg_connection *lsn,
struct pkt *pkt) {
struct mg_connection *c = mg_alloc_conn(lsn->mgr);
if (c == NULL) {
MG_ERROR(("OOM"));
return NULL;
}
struct connstate *s = (struct connstate *) (c + 1);
s->seq = mg_ntohl(pkt->tcp->ack), s->ack = mg_ntohl(pkt->tcp->seq);
memcpy(s->mac, pkt->eth->src, sizeof(s->mac));
settmout(c, MIP_TTYPE_KEEPALIVE);
memcpy(c->rem.ip, &pkt->ip->src, sizeof(uint32_t));
c->rem.port = pkt->tcp->sport;
MG_DEBUG(("%lu accepted %M", c->id, mg_print_ip_port, &c->rem));
LIST_ADD_HEAD(struct mg_connection, &lsn->mgr->conns, c);
c->is_accepted = 1;
c->is_hexdumping = lsn->is_hexdumping;
c->pfn = lsn->pfn;
c->loc = lsn->loc;
c->pfn_data = lsn->pfn_data;
c->fn = lsn->fn;
c->fn_data = lsn->fn_data;
mg_call(c, MG_EV_OPEN, NULL);
mg_call(c, MG_EV_ACCEPT, NULL);
return c;
}
static size_t trim_len(struct mg_connection *c, size_t len) {
struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->mgr->priv;
size_t eth_h_len = 14, ip_max_h_len = 24, tcp_max_h_len = 60, udp_h_len = 8;
size_t max_headers_len =
eth_h_len + ip_max_h_len + (c->is_udp ? udp_h_len : tcp_max_h_len);
size_t min_mtu = c->is_udp ? 68 /* RFC-791 */ : max_headers_len - eth_h_len;
// If the frame exceeds the available buffer, trim the length
if (len + max_headers_len > ifp->tx.len) {
len = ifp->tx.len - max_headers_len;
}
// Ensure the MTU isn't lower than the minimum allowed value
if (ifp->mtu < min_mtu) {
MG_ERROR(("MTU is lower than minimum, capping to %lu", min_mtu));
ifp->mtu = (uint16_t) min_mtu;
}
// If the total packet size exceeds the MTU, trim the length
if (len + max_headers_len - eth_h_len > ifp->mtu) {
len = ifp->mtu - max_headers_len + eth_h_len;
if (c->is_udp) {
MG_ERROR(("UDP datagram exceeds MTU. Truncating it."));
}
}
return len;
}
long mg_io_send(struct mg_connection *c, const void *buf, size_t len) {
struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->mgr->priv;
struct connstate *s = (struct connstate *) (c + 1);
uint32_t dst_ip = *(uint32_t *) c->rem.ip;
len = trim_len(c, len);
if (c->is_udp) {
tx_udp(ifp, s->mac, ifp->ip, c->loc.port, dst_ip, c->rem.port, buf, len);
} else {
size_t sent =
tx_tcp(ifp, s->mac, dst_ip, TH_PUSH | TH_ACK, c->loc.port, c->rem.port,
mg_htonl(s->seq), mg_htonl(s->ack), buf, len);
if (sent == 0) {
return MG_IO_WAIT;
} else if (sent == (size_t) -1) {
return MG_IO_ERR;
} else {
s->seq += (uint32_t) len;
if (s->ttype == MIP_TTYPE_ACK) settmout(c, MIP_TTYPE_KEEPALIVE);
}
}
return (long) len;
}
static void handle_tls_recv(struct mg_connection *c, struct mg_iobuf *io) {
long n = mg_tls_recv(c, &io->buf[io->len], io->size - io->len);
if (n == MG_IO_ERR) {
mg_error(c, "TLS recv error");
} else if (n > 0) {
// Decrypted successfully - trigger MG_EV_READ
io->len += (size_t) n;
mg_call(c, MG_EV_READ, &n);
}
}
static void read_conn(struct mg_connection *c, struct pkt *pkt) {
struct connstate *s = (struct connstate *) (c + 1);
struct mg_iobuf *io = c->is_tls ? &c->rtls : &c->recv;
uint32_t seq = mg_ntohl(pkt->tcp->seq);
uint32_t rem_ip;
memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));
if (pkt->tcp->flags & TH_FIN) {
// If we initiated the closure, we reply with ACK upon receiving FIN
// If we didn't initiate it, we reply with FIN as part of the normal TCP
// closure process
uint8_t flags = TH_ACK;
s->ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len + 1);
if (c->is_draining && s->ttype == MIP_TTYPE_FIN) {
if (s->seq == mg_htonl(pkt->tcp->ack)) { // Simultaneous closure ?
s->seq++; // Yes. Increment our SEQ
} else { // Otherwise,
s->seq = mg_htonl(pkt->tcp->ack); // Set to peer's ACK
}
} else {
flags |= TH_FIN;
c->is_draining = 1;
settmout(c, MIP_TTYPE_FIN);
}
tx_tcp((struct mg_tcpip_if *) c->mgr->priv, s->mac, rem_ip, flags,
c->loc.port, c->rem.port, mg_htonl(s->seq), mg_htonl(s->ack), "", 0);
} else if (pkt->pay.len == 0) {
// TODO(cpq): handle this peer's ACK
} else if (seq != s->ack) {
uint32_t ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len);
if (s->ack == ack) {
MG_VERBOSE(("ignoring duplicate pkt"));
} else {
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);
}
} else if (io->size - io->len < pkt->pay.len &&
!mg_iobuf_resize(io, io->len + pkt->pay.len)) {
mg_error(c, "oom");
} else {
// Copy TCP payload into the IO buffer. If the connection is plain text,
// we copy to c->recv. If the connection is TLS, this data is encrypted,
// therefore we copy that encrypted data to the c->rtls iobuffer instead,
// and then call mg_tls_recv() to decrypt it. NOTE: mg_tls_recv() will
// call back mg_io_recv() which grabs raw data from c->rtls
memcpy(&io->buf[io->len], pkt->pay.buf, pkt->pay.len);
io->len += pkt->pay.len;
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);
s->unacked += pkt->pay.len;
// size_t diff = s->acked <= s->ack ? s->ack - s->acked : s->ack;
if (s->unacked > MIP_TCP_WIN / 2 && s->acked != s->ack) {
// Send ACK immediately
MG_VERBOSE(("%lu imm ACK %lu", c->id, s->acked));
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), NULL,
0);
s->unacked = 0;
s->acked = s->ack;
if (s->ttype != MIP_TTYPE_KEEPALIVE) settmout(c, MIP_TTYPE_KEEPALIVE);
} else {
// if not already running, setup a timer to send an ACK later
if (s->ttype != MIP_TTYPE_ACK) settmout(c, MIP_TTYPE_ACK);
}
if (c->is_tls && c->is_tls_hs) {
mg_tls_handshake(c);
} else if (c->is_tls) {
// TLS connection. Make room for decrypted data in c->recv
io = &c->recv;
if (io->size - io->len < pkt->pay.len &&
!mg_iobuf_resize(io, io->len + pkt->pay.len)) {
mg_error(c, "oom");
} else {
// Decrypt data directly into c->recv
handle_tls_recv(c, io);
}
} else {
// Plain text connection, data is already in c->recv, trigger
// MG_EV_READ
mg_call(c, MG_EV_READ, &pkt->pay.len);
}
}
}
static void rx_tcp(struct mg_tcpip_if *ifp, struct pkt *pkt) {
struct mg_connection *c = getpeer(ifp->mgr, pkt, false);
struct connstate *s = c == NULL ? NULL : (struct connstate *) (c + 1);
#if 0
MG_INFO(("%lu %hhu %d", c ? c->id : 0, pkt->tcp->flags, (int) pkt->pay.len));
#endif
if (c != NULL && c->is_connecting && pkt->tcp->flags == (TH_SYN | TH_ACK)) {
s->seq = mg_ntohl(pkt->tcp->ack), s->ack = mg_ntohl(pkt->tcp->seq) + 1;
tx_tcp_pkt(ifp, pkt, TH_ACK, pkt->tcp->ack, NULL, 0);
c->is_connecting = 0; // Client connected
settmout(c, MIP_TTYPE_KEEPALIVE);
mg_call(c, MG_EV_CONNECT, NULL); // Let user know
if (c->is_tls_hs) mg_tls_handshake(c);
} else if (c != NULL && c->is_connecting && pkt->tcp->flags != TH_ACK) {
// mg_hexdump(pkt->raw.buf, 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
} else if (c != NULL) {
#if 0
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);
#endif
s->tmiss = 0; // Reset missed keep-alive counter
if (s->ttype == MIP_TTYPE_KEEPALIVE) // Advance keep-alive timer
settmout(c,
MIP_TTYPE_KEEPALIVE); // unless a former ACK timeout is pending
read_conn(c, pkt); // Override timer with ACK timeout if needed
} else if ((c = getpeer(ifp->mgr, pkt, true)) == NULL) {
tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
} else if (pkt->tcp->flags & TH_RST) {
if (c->is_accepted) mg_error(c, "peer RST"); // RFC-1122 4.2.2.13
// ignore RST if not connected
} else if (pkt->tcp->flags & TH_SYN) {
// Use peer's source port as ISN, in order to recognise the handshake
uint32_t isn = mg_htonl((uint32_t) mg_ntohs(pkt->tcp->sport));
tx_tcp_pkt(ifp, pkt, TH_SYN | TH_ACK, isn, NULL, 0);
} else if (pkt->tcp->flags & TH_FIN) {
tx_tcp_pkt(ifp, pkt, TH_FIN | TH_ACK, pkt->tcp->ack, NULL, 0);
} else if (mg_htonl(pkt->tcp->ack) == mg_htons(pkt->tcp->sport) + 1U) {
accept_conn(c, pkt);
} else if (!c->is_accepted) { // no peer
tx_tcp_pkt(ifp, pkt, TH_RST | TH_ACK, pkt->tcp->ack, NULL, 0);
} else {
// MG_VERBOSE(("dropped silently.."));
}
}
static void rx_ip(struct mg_tcpip_if *ifp, struct pkt *pkt) {
if (pkt->ip->frag & IP_MORE_FRAGS_MSK || pkt->ip->frag & IP_FRAG_OFFSET_MSK) {
if (pkt->ip->proto == 17) pkt->udp = (struct udp *) (pkt->ip + 1);
if (pkt->ip->proto == 6) pkt->tcp = (struct tcp *) (pkt->ip + 1);
struct mg_connection *c = getpeer(ifp->mgr, pkt, false);
if (c) mg_error(c, "Received fragmented packet");
} else if (pkt->ip->proto == 1) {
pkt->icmp = (struct icmp *) (pkt->ip + 1);
if (pkt->pay.len < sizeof(*pkt->icmp)) return;
mkpay(pkt, pkt->icmp + 1);
rx_icmp(ifp, pkt);
} else if (pkt->ip->proto == 17) {
pkt->udp = (struct udp *) (pkt->ip + 1);
if (pkt->pay.len < sizeof(*pkt->udp)) return;
mkpay(pkt, pkt->udp + 1);
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);
rx_dhcp_client(ifp, pkt);
} else if (ifp->enable_dhcp_server && pkt->udp->dport == mg_htons(67)) {
pkt->dhcp = (struct dhcp *) (pkt->udp + 1);
mkpay(pkt, pkt->dhcp + 1);
rx_dhcp_server(ifp, pkt);
} else {
rx_udp(ifp, pkt);
}
} else if (pkt->ip->proto == 6) {
pkt->tcp = (struct tcp *) (pkt->ip + 1);
if (pkt->pay.len < sizeof(*pkt->tcp)) return;
mkpay(pkt, pkt->tcp + 1);
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_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);
}
}
static void rx_ip6(struct mg_tcpip_if *ifp, struct pkt *pkt) {
// MG_DEBUG(("IP %d", (int) len));
if (pkt->ip6->proto == 1 || pkt->ip6->proto == 58) {
pkt->icmp = (struct icmp *) (pkt->ip6 + 1);
if (pkt->pay.len < sizeof(*pkt->icmp)) return;
mkpay(pkt, pkt->icmp + 1);
rx_icmp(ifp, pkt);
} else if (pkt->ip6->proto == 17) {
pkt->udp = (struct udp *) (pkt->ip6 + 1);
if (pkt->pay.len < sizeof(*pkt->udp)) return;
// MG_DEBUG((" UDP %u %u -> %u", len, mg_htons(udp->sport),
// mg_htons(udp->dport)));
mkpay(pkt, pkt->udp + 1);
}
}
static void mg_tcpip_rx(struct mg_tcpip_if *ifp, void *buf, size_t len) {
struct pkt pkt;
memset(&pkt, 0, sizeof(pkt));
pkt.raw.buf = (char *) buf;
pkt.raw.len = len;
pkt.eth = (struct eth *) buf;
// mg_hexdump(buf, len > 16 ? 16: len);
if (pkt.raw.len < sizeof(*pkt.eth)) return; // Truncated - runt?
if (ifp->enable_mac_check &&
memcmp(pkt.eth->dst, ifp->mac, sizeof(pkt.eth->dst)) != 0 &&
memcmp(pkt.eth->dst, broadcast, sizeof(pkt.eth->dst)) != 0)
return;
if (ifp->enable_crc32_check && len > 4) {
len -= 4; // TODO(scaprile): check on bigendian
uint32_t crc = mg_crc32(0, (const char *) buf, len);
if (memcmp((void *) ((size_t) buf + len), &crc, sizeof(crc))) return;
}
if (pkt.eth->type == mg_htons(0x806)) {
pkt.arp = (struct arp *) (pkt.eth + 1);
if (sizeof(*pkt.eth) + sizeof(*pkt.arp) > pkt.raw.len) return; // Truncated
rx_arp(ifp, &pkt);
} else if (pkt.eth->type == mg_htons(0x86dd)) {
pkt.ip6 = (struct ip6 *) (pkt.eth + 1);
if (pkt.raw.len < sizeof(*pkt.eth) + sizeof(*pkt.ip6)) return; // Truncated
if ((pkt.ip6->ver >> 4) != 0x6) return; // Not IP
mkpay(&pkt, pkt.ip6 + 1);
rx_ip6(ifp, &pkt);
} else if (pkt.eth->type == mg_htons(0x800)) {
pkt.ip = (struct ip *) (pkt.eth + 1);
if (pkt.raw.len < sizeof(*pkt.eth) + sizeof(*pkt.ip)) return; // Truncated
// Truncate frame to what IP header tells us
if ((size_t) mg_ntohs(pkt.ip->len) + sizeof(struct eth) < pkt.raw.len) {
pkt.raw.len = (size_t) mg_ntohs(pkt.ip->len) + sizeof(struct eth);
}
if (pkt.raw.len < sizeof(*pkt.eth) + sizeof(*pkt.ip)) return; // Truncated
if ((pkt.ip->ver >> 4) != 4) return; // Not IP
mkpay(&pkt, pkt.ip + 1);
rx_ip(ifp, &pkt);
} else {
MG_DEBUG(("Unknown eth type %x", mg_htons(pkt.eth->type)));
if (mg_log_level >= MG_LL_VERBOSE) mg_hexdump(buf, len >= 32 ? 32 : len);
}
}
static void mg_tcpip_poll(struct mg_tcpip_if *ifp, uint64_t now) {
struct mg_connection *c;
bool expired_1000ms = mg_timer_expired(&ifp->timer_1000ms, 1000, now);
ifp->now = now;
#if MG_ENABLE_TCPIP_PRINT_DEBUG_STATS
if (expired_1000ms) {
const char *names[] = {"down", "up", "req", "ready"};
MG_INFO(("Status: %s, IP: %M, rx:%u, tx:%u, dr:%u, er:%u",
names[ifp->state], mg_print_ip4, &ifp->ip, ifp->nrecv, ifp->nsent,
ifp->ndrop, ifp->nerr));
}
#endif
// Handle physical interface up/down status
if (expired_1000ms && ifp->driver->up) {
bool up = ifp->driver->up(ifp);
bool current = ifp->state != MG_TCPIP_STATE_DOWN;
if (up != current) {
ifp->state = up == false ? MG_TCPIP_STATE_DOWN
: ifp->enable_dhcp_client ? MG_TCPIP_STATE_UP
: MG_TCPIP_STATE_READY;
if (!up && ifp->enable_dhcp_client) ifp->ip = 0;
onstatechange(ifp);
}
if (ifp->state == MG_TCPIP_STATE_DOWN) MG_ERROR(("Network is down"));
}
if (ifp->state == MG_TCPIP_STATE_DOWN) return;
// DHCP RFC-2131 (4.4)
if (ifp->state == MG_TCPIP_STATE_UP && expired_1000ms) {
tx_dhcp_discover(ifp); // INIT (4.4.1)
} else if (expired_1000ms && ifp->state == MG_TCPIP_STATE_READY &&
ifp->lease_expire > 0) { // BOUND / RENEWING / REBINDING
if (ifp->now >= ifp->lease_expire) {
ifp->state = MG_TCPIP_STATE_UP, ifp->ip = 0; // expired, release IP
onstatechange(ifp);
} else if (ifp->now + 30UL * 60UL * 1000UL > ifp->lease_expire &&
((ifp->now / 1000) % 60) == 0) {
// hack: 30 min before deadline, try to rebind (4.3.6) every min
tx_dhcp_request_re(ifp, (uint8_t *) broadcast, ifp->ip, 0xffffffff);
} // TODO(): Handle T1 (RENEWING) and T2 (REBINDING) (4.4.5)
}
// Read data from the network
if (ifp->driver->rx != NULL) { // Polling driver. We must call it
size_t len =
ifp->driver->rx(ifp->recv_queue.buf, ifp->recv_queue.size, ifp);
if (len > 0) {
ifp->nrecv++;
mg_tcpip_rx(ifp, ifp->recv_queue.buf, len);
}
} else { // Interrupt-based driver. Fills recv queue itself
char *buf;
size_t len = mg_queue_next(&ifp->recv_queue, &buf);
if (len > 0) {
mg_tcpip_rx(ifp, buf, len);
mg_queue_del(&ifp->recv_queue, len);
}
}
// Process timeouts
for (c = ifp->mgr->conns; c != NULL; c = c->next) {
if (c->is_udp || c->is_listening || c->is_resolving) continue;
struct connstate *s = (struct connstate *) (c + 1);
uint32_t rem_ip;
memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));
if (now > s->timer) {
if (s->ttype == MIP_TTYPE_ACK && s->acked != 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), NULL, 0);
s->acked = s->ack;
} else if (s->ttype == MIP_TTYPE_ARP) {
mg_error(c, "ARP timeout");
} else if (s->ttype == MIP_TTYPE_SYN) {
mg_error(c, "Connection timeout");
} else if (s->ttype == MIP_TTYPE_FIN) {
c->is_closing = 1;
continue;
} else {
if (s->tmiss++ > 2) {
mg_error(c, "keepalive");
} else {
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), NULL, 0);
}
}
settmout(c, MIP_TTYPE_KEEPALIVE);
}
}
}
// This function executes in interrupt context, thus it should copy data
// somewhere fast. Note that newlib's malloc is not thread safe, thus use
// our lock-free queue with preallocated buffer to copy data and return asap
void mg_tcpip_qwrite(void *buf, size_t len, struct mg_tcpip_if *ifp) {
char *p;
if (mg_queue_book(&ifp->recv_queue, &p, len) >= len) {
memcpy(p, buf, len);
mg_queue_add(&ifp->recv_queue, len);
ifp->nrecv++;
} else {
ifp->ndrop++;
}
}
void mg_tcpip_init(struct mg_mgr *mgr, struct mg_tcpip_if *ifp) {
// If MAC address is not set, make a random one
if (ifp->mac[0] == 0 && ifp->mac[1] == 0 && ifp->mac[2] == 0 &&
ifp->mac[3] == 0 && ifp->mac[4] == 0 && ifp->mac[5] == 0) {
ifp->mac[0] = 0x02; // Locally administered, unicast