TCP: Delay ACKs to batch together packets ACKed

4 files changed, 33 insertions, 1 deletions

diff --git a/kernel/drivers/pit.c b/kernel/drivers/pit.c
index 80f55aa..db9cd2a 100644
--- a/kernel/drivers/pit.c
+++ b/kernel/drivers/pit.c
@@ -43,10 +43,16 @@ void set_pit_count(u16 _hertz) {
   outb(PIT_IO_CHANNEL_0, (divisor & 0xFF00) >> 8);
 }
 
+int last_flush = 0;
+
 extern int is_switching_tasks;
 void int_clock(reg_t *regs) {
   clock_num_ms_ticks += 5;
   switch_counter++;
+  if (clock_num_ms_ticks - last_flush > 50) {
+    tcp_flush_acks();
+    last_flush = clock_num_ms_ticks;
+  }
   if (switch_counter >= hertz) {
     EOI(0x20);
     switch_counter = 0;
diff --git a/kernel/network/tcp.c b/kernel/network/tcp.c
index bb48f53..e6febba 100644
--- a/kernel/network/tcp.c
+++ b/kernel/network/tcp.c
@@ -84,6 +84,7 @@ void tcp_send_empty_payload(struct TcpConnection *con, u8 flags) {
   header.dst_port = htons(con->outgoing_port);
   header.seq_num = htonl(con->snd_nxt);
   if (flags & ACK) {
+    con->should_send_ack = 0;
     header.ack_num = htonl(con->rcv_nxt);
   } else {
     header.ack_num = 0;
@@ -282,7 +283,7 @@ void handle_tcp(ipv4_t src_ip, ipv4_t dst_ip, const u8 *payload,
       int rc = ringbuffer_write(&con->incoming_buffer, tcp_payload,
                                 tcp_payload_length);
       con->rcv_nxt += rc;
-      tcp_send_empty_payload(con, ACK);
+      con->should_send_ack = 1;
     }
     break;
   }
diff --git a/kernel/socket.c b/kernel/socket.c
index bd7f755..54f7598 100644
--- a/kernel/socket.c
+++ b/kernel/socket.c
@@ -72,6 +72,27 @@ struct TcpConnection *tcp_find_connection(ipv4_t src_ip, u16 src_port,
   return NULL;
 }
 
+void tcp_flush_acks(void) {
+  for (int i = 0;; i++) {
+    struct TcpConnection *c;
+    int end;
+    if (!relist_get(&open_tcp_connections, i, (void **)&c, &end)) {
+      if (end) {
+        break;
+      }
+      continue;
+    }
+    if (TCP_STATE_CLOSED == c->state) {
+      continue;
+    }
+    if (!c->should_send_ack) {
+      continue;
+    }
+    c->should_send_ack = 0;
+    tcp_send_empty_payload(c, ACK);
+  }
+}
+
 u16 tcp_find_free_port(u16 suggestion) {
   for (int i = 0;; i++) {
     struct TcpConnection *c;
@@ -580,6 +601,7 @@ int tcp_create_fd(int is_nonblock) {
     return -ENOMEM;
   }
   con->state = TCP_STATE_CLOSED;
+  con->should_send_ack = 0;
 
   vfs_inode_t *inode = vfs_create_inode(
       0 /*inode_num*/, FS_TYPE_UNIX_SOCKET, NULL, always_can_write, 1, con,
diff --git a/kernel/socket.h b/kernel/socket.h
index 454992c..e881111 100644
--- a/kernel/socket.h
+++ b/kernel/socket.h
@@ -64,6 +64,8 @@ struct TcpConnection {
   u32 rcv_nxt;
   u32 rcv_adv;
 
+  int should_send_ack;
+
   u32 snd_una;
   u32 snd_nxt;
   u32 snd_max;
@@ -142,4 +144,5 @@ u16 tcp_get_free_port(void);
 int setsockopt(int socket, int level, int option_name, const void *option_value,
                socklen_t option_len);
 void tcp_remove_connection(struct TcpConnection *con);
+void tcp_flush_acks(void);
 #endif