[PATCH] dont increase the size of socket buffers in low memory situations

[Simon Mages]

At the moment the buffersize will be set to the default even if the
current value
is smaller.

The following diff fixes this problem.

Index: netinet/tcp_usrreq.c
===================================================================
RCS file: /cvs/src/sys/netinet/tcp_usrreq.c,v
retrieving revision 1.131
diff -u -p -u -p -r1.131 tcp_usrreq.c
--- netinet/tcp_usrreq.c        18 Jun 2016 10:36:13 -0000      1.131
+++ netinet/tcp_usrreq.c        5 Jul 2016 09:26:24 -0000
@@ -979,10 +979,11 @@ tcp_update_sndspace(struct tcpcb *tp)
        struct socket *so = tp->t_inpcb->inp_socket;
        u_long nmax;

-       if (sbchecklowmem())
+       if (sbchecklowmem()) {
                /* low on memory try to get rid of some */
-               nmax = tcp_sendspace;
-       else if (so->so_snd.sb_wat != tcp_sendspace)
+               if (so->so_snd.sb_hiwat < nmax)
+                       nmax = tcp_sendspace;
+       } else if (so->so_snd.sb_wat != tcp_sendspace)
                /* user requested buffer size, auto-scaling disabled */
                nmax = so->so_snd.sb_wat;
        else
@@ -1017,10 +1018,11 @@ tcp_update_rcvspace(struct tcpcb *tp)
        struct socket *so = tp->t_inpcb->inp_socket;
        u_long nmax = so->so_rcv.sb_hiwat;

-       if (sbchecklowmem())
+       if (sbchecklowmem()) {
                /* low on memory try to get rid of some */
-               nmax = tcp_recvspace;
-       else if (so->so_rcv.sb_wat != tcp_recvspace)
+               if (tcp_recvspace < nmax)
+                       nmax = tcp_recvspace;
+       } else if (so->so_rcv.sb_wat != tcp_recvspace)
                /* user requested buffer size, auto-scaling disabled */
                nmax = so->so_rcv.sb_wat;
        else {