[NET]: Size listen hash tables using backlog hint

We currently allocate a fixed size (TCP_SYNQ_HSIZE=512) slots hash table for
each LISTEN socket, regardless of various parameters (listen backlog for
example)

On x86_64, this means order-1 allocations (might fail), even for 'small'
sockets, expecting few connections. On the contrary, a huge server wanting a
backlog of 50000 is slowed down a bit because of this fixed limit.

This patch makes the sizing of listen hash table a dynamic parameter,
depending of :
- net.core.somaxconn tunable (default is 128)
- net.ipv4.tcp_max_syn_backlog tunable (default : 256, 1024 or 128)
- backlog value given by user application  (2nd parameter of listen())

For large allocations (bigger than PAGE_SIZE), we use vmalloc() instead of
kmalloc().

We still limit memory allocation with the two existing tunables (somaxconn &
tcp_max_syn_backlog). So for standard setups, this patch actually reduce RAM
usage.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 22ef8bd..5fbf965 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -715,7 +715,7 @@ static struct ip_options *tcp_v4_save_options(struct sock *sk,
 	return dopt;
 }
 
-struct request_sock_ops tcp_request_sock_ops = {
+struct request_sock_ops tcp_request_sock_ops __read_mostly = {
 	.family		=	PF_INET,
 	.obj_size	=	sizeof(struct tcp_request_sock),
 	.rtx_syn_ack	=	tcp_v4_send_synack,
@@ -1385,7 +1385,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
 	if (st->state == TCP_SEQ_STATE_OPENREQ) {
 		struct request_sock *req = cur;
 
-	       	icsk = inet_csk(st->syn_wait_sk);
+		icsk = inet_csk(st->syn_wait_sk);
 		req = req->dl_next;
 		while (1) {
 			while (req) {
@@ -1395,7 +1395,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
 				}
 				req = req->dl_next;
 			}
-			if (++st->sbucket >= TCP_SYNQ_HSIZE)
+			if (++st->sbucket >= icsk->icsk_accept_queue.listen_opt->nr_table_entries)
 				break;
 get_req:
 			req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];