Allocate a persistent packet buffer.

Instead of allocating a new packet buffer every time we generate a packet,
we pre-allocate it and keep it around. We only reallocate when the MTU
increases.

diff --git a/utcp.c b/utcp.c
index 5d630694df96100f57e780f855a32cc63f7674bc..ae3b2b6da469a56804ea07c2727c7855e6bffb8d 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -527,13 +527,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
        struct {
                struct hdr hdr;
                uint8_t data[];
-       } *pkt;
-
-       pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-       if(!pkt) {
-               return;
-       }
+       } *pkt = c->utcp->pkt;
 
        pkt->hdr.src = c->src;
        pkt->hdr.dst = c->dst;
@@ -566,8 +560,6 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
                print_packet(c->utcp, "send", pkt, sizeof(pkt->hdr) + seglen);
                c->utcp->send(c->utcp, pkt, sizeof(pkt->hdr) + seglen);
        } while(left);
-
-       free(pkt);
 }
 
 ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
@@ -687,13 +679,7 @@ static void retransmit(struct utcp_connection *c) {
        struct {
                struct hdr hdr;
                uint8_t data[];
-       } *pkt;
-
-       pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-       if(!pkt) {
-               return;
-       }
+       } *pkt = c->utcp->pkt;
 
        pkt->hdr.src = c->src;
        pkt->hdr.dst = c->dst;
@@ -773,7 +759,7 @@ static void retransmit(struct utcp_connection *c) {
        c->rtt_start.tv_sec = 0; // invalidate RTT timer
 
 cleanup:
-       free(pkt);
+       return;
 }
 
 /* Update receive buffer and SACK entries after consuming data.
@@ -1861,7 +1847,7 @@ struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_
        utcp->pre_accept = pre_accept;
        utcp->send = send;
        utcp->priv = priv;
-       utcp->mtu = DEFAULT_MTU;
+       utcp_set_mtu(utcp, DEFAULT_MTU);
        utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
        utcp->rto = START_RTO; // usec
 
@@ -1900,10 +1886,22 @@ uint16_t utcp_get_mtu(struct utcp *utcp) {
 }
 
 void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
-       // TODO: handle overhead of the header
-       if(utcp) {
-               utcp->mtu = mtu;
+       if (!utcp) {
+               return;
        }
+
+       if (mtu <= sizeof(struct hdr)) {
+               return;
+       }
+
+       if (mtu > utcp->mtu) {
+               char *new = realloc(utcp->pkt, mtu);
+               if (!new)
+                       return;
+               utcp->pkt = new;
+       }
+
+       utcp->mtu = mtu;
 }
 
 void utcp_reset_timers(struct utcp *utcp) {

diff --git a/utcp_priv.h b/utcp_priv.h
index 6c5c1f85f052016999b800534e398a21884eec17..1f72fb482c9c7b5140ab730936c738561ad88ab6 100644 (file)
--- a/utcp_priv.h
+++ b/utcp_priv.h
@@ -169,6 +169,10 @@ struct utcp {
        utcp_pre_accept_t pre_accept;
        utcp_send_t send;
 
+       // Packet buffer
+
+       void *pkt;
+
        // Global socket options
 
        uint16_t mtu;