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 50c7e364a33b2ee68a8b5d95b5bdb3d106287756..f7d18b9f89c736050f3fcb29104aec22c316c49a 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -549,13 +549,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
        struct {
                struct hdr hdr;
                uint8_t data[];
-       } *pkt;
-
-       pkt = malloc(c->utcp->mtu);
-
-       if(!pkt) {
-               return;
-       }
+       } *pkt = c->utcp->pkt;
 
        pkt->hdr.src = c->src;
        pkt->hdr.dst = c->dst;
@@ -588,8 +582,6 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
                print_packet(c, "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) {
@@ -762,13 +754,7 @@ static void retransmit(struct utcp_connection *c) {
        struct {
                struct hdr hdr;
                uint8_t data[];
-       } *pkt;
-
-       pkt = malloc(c->utcp->mtu);
-
-       if(!pkt) {
-               return;
-       }
+       } *pkt = c->utcp->pkt;
 
        pkt->hdr.src = c->src;
        pkt->hdr.dst = c->dst;
@@ -851,7 +837,7 @@ static void retransmit(struct utcp_connection *c) {
        c->dupack = 0; // cancel any ongoing fast recovery
 
 cleanup:
-       free(pkt);
+       return;
 }
 
 /* Update receive buffer and SACK entries after consuming data.
@@ -1991,8 +1977,7 @@ 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->mss = DEFAULT_MTU - sizeof(struct hdr);
+       utcp_set_mtu(utcp, DEFAULT_MTU);
        utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
        utcp->rto = START_RTO; // usec
 
@@ -2031,11 +2016,23 @@ 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;
-               utcp->mss = mtu - sizeof(struct hdr);
+       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;
+       utcp->mss = mtu - sizeof(struct hdr);
 }
 
 void utcp_reset_timers(struct utcp *utcp) {

diff --git a/utcp_priv.h b/utcp_priv.h
index de942a8968ae61ef27592126244ad935dcfe5475..49ff4bff47bf3f432d3a027f85d8656286a2eb08 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; // The maximum size of a UTCP packet, including headers.