Fix SYN packet handling.

This fixes problems with SYN packets arriving out of the usual order.
This also adds a more proper handling of the aux field.

diff --git a/utcp.c b/utcp.c
index 02d3c983ba75d3ad1dc9ea1447ebaa64588bf9b5..340b059a6917e2738242b4292439a407924cc003 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -75,7 +75,7 @@ static void print_packet(struct utcp *utcp, const char *dir, const void *pkt, si
        }
 
        memcpy(&hdr, pkt, sizeof hdr);
-       debug("%p %s: len=%lu, src=%u dst=%u seq=%u ack=%u wnd=%u ctl=", utcp, dir, (unsigned long)len, hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd);
+       debug("%p %s: len=%lu, src=%u dst=%u seq=%u ack=%u wnd=%u aux=%x ctl=", utcp, dir, (unsigned long)len, hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd, hdr.aux);
        if(hdr.ctl & SYN)
                debug("SYN");
        if(hdr.ctl & RST)
@@ -457,7 +457,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 
        struct {
                struct hdr hdr;
-               char data[];
+               uint8_t data[];
        } *pkt;
 
        pkt = malloc(sizeof pkt->hdr + c->utcp->mtu);
@@ -573,7 +573,7 @@ static void retransmit(struct utcp_connection *c) {
 
        struct {
                struct hdr hdr;
-               char data[];
+               uint8_t data[];
        } *pkt;
 
        pkt = malloc(sizeof pkt->hdr + c->utcp->mtu);
@@ -828,6 +828,49 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                return -1;
        }
 
+       // Check for auxiliary headers
+
+       const uint8_t *init = NULL;
+
+       uint16_t aux = hdr.aux;
+       while(aux) {
+               size_t auxlen = 4 * (aux >> 8) & 0xf;
+               uint8_t auxtype = aux & 0xff;
+
+               if(len < auxlen) {
+                       errno = EBADMSG;
+                       return -1;
+               }
+
+               switch(auxtype) {
+               case AUX_INIT:
+                       if(!(hdr.ctl & SYN) || auxlen != 4) {
+                               errno = EBADMSG;
+                               return -1;
+                       }
+                       init = data;
+                       break;
+               default:
+                       errno = EBADMSG;
+                       return -1;
+               }
+
+               len -= auxlen;
+               data += auxlen;
+
+               if(!(aux & 0x800))
+                       break;
+
+               if(len < 2) {
+                       errno = EBADMSG;
+                       return -1;
+               }
+
+               memcpy(&aux, data, 2);
+               len -= 2;
+               data += 2;
+       }
+
        // Try to match the packet to an existing connection
 
        struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
@@ -857,14 +900,12 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                        }
 
                        // Parse auxilliary information
-                       if(hdr.aux) {
-                               if(hdr.aux != 0x0101 || len < 4 || ((uint8_t *)data)[0] != 1) {
+                       if(init) {
+                               if(init[0] < 1) {
                                        len = 1;
                                        goto reset;
                                }
-                               c->flags = ((uint8_t *)data)[3] & 0x7;
-                               data += 4;
-                               len -= 4;
+                               c->flags = init[3] & 0x7;
                        } else {
                                c->flags = UTCP_TCP;
                        }
@@ -875,13 +916,30 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                        c->rcv.nxt = c->rcv.irs + 1;
                        set_state(c, SYN_RECEIVED);
 
-                       hdr.dst = c->dst;
-                       hdr.src = c->src;
-                       hdr.ack = c->rcv.irs + 1;
-                       hdr.seq = c->snd.iss;
-                       hdr.ctl = SYN | ACK;
-                       print_packet(c->utcp, "send", &hdr, sizeof hdr);
-                       utcp->send(utcp, &hdr, sizeof hdr);
+                       struct {
+                               struct hdr hdr;
+                               uint8_t data[4];
+                       } pkt;
+
+                       pkt.hdr.src = c->src;
+                       pkt.hdr.dst = c->dst;
+                       pkt.hdr.ack = c->rcv.irs + 1;
+                       pkt.hdr.seq = c->snd.iss;
+                       pkt.hdr.wnd = c->rcv.wnd;
+                       pkt.hdr.ctl = SYN | ACK;
+                       if(init) {
+                               pkt.hdr.aux = 0x0101;
+                               pkt.data[0] = 1;
+                               pkt.data[1] = 0;
+                               pkt.data[2] = 0;
+                               pkt.data[3] = c->flags & 0x7;
+                               print_packet(c->utcp, "send", &pkt, sizeof hdr + 4);
+                               utcp->send(utcp, &pkt, sizeof hdr + 4);
+                       } else {
+                               pkt.hdr.aux = 0;
+                               print_packet(c->utcp, "send", &pkt, sizeof hdr);
+                               utcp->send(utcp, &pkt, sizeof hdr);
+                       }
                } else {
                        // No, we don't want your packets, send a RST back
                        len = 1;
@@ -1027,6 +1085,9 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                }
        }
 
+       if(!(hdr.ctl & ACK))
+               goto skip_ack;
+
        // 3. Advance snd.una
 
        uint32_t advanced = seqdiff(hdr.ack, c->snd.una);
@@ -1119,6 +1180,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                        start_retransmit_timer(c);
        }
 
+skip_ack:
        // 5. Process SYN stuff
 
        if(hdr.ctl & SYN) {
@@ -1141,7 +1203,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                case LAST_ACK:
                case TIME_WAIT:
                        // Ehm, no. We should never receive a second SYN.
-                       goto reset;
+                       return 0;
                default:
 #ifdef UTCP_DEBUG
                        abort();
@@ -1258,6 +1320,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 reset:
        swap_ports(&hdr);
        hdr.wnd = 0;
+       hdr.aux = 0;
        if(hdr.ctl & ACK) {
                hdr.seq = hdr.ack;
                hdr.ctl = RST;

diff --git a/utcp_priv.h b/utcp_priv.h
index fa706bcf84bcad5eed5e825bf3c7bc671cd51542..437941f61b126c49560e0b30f54ad651981d0b94 100644 (file)
--- a/utcp_priv.h
+++ b/utcp_priv.h
@@ -30,6 +30,11 @@
 #define FIN 4
 #define RST 8
 
+#define AUX_INIT 1
+#define AUX_FRAME 2
+#define AUX_SAK 3
+#define AUX_TIMESTAMP 4
+
 #define NSACKS 4
 #define DEFAULT_SNDBUFSIZE 4096
 #define DEFAULT_MAXSNDBUFSIZE 131072