net/rxrpc/output.c

   1 /* RxRPC packet transmission
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/net.h>
  15 #include <linux/gfp.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/export.h>
  18 #include <net/sock.h>
  19 #include <net/af_rxrpc.h>
  20 #include "ar-internal.h"
  21
  22 /*
  23  * send a packet through the transport endpoint
  24  */
  25 int rxrpc_send_data_packet(struct rxrpc_connection *conn, struct sk_buff *skb)
  26 {
  27         struct kvec iov[1];
  28         struct msghdr msg;
  29         int ret, opt;
  30
  31         _enter(",{%d}", skb->len);
  32
  33         iov[0].iov_base = skb->head;
  34         iov[0].iov_len = skb->len;
  35
  36         msg.msg_name = &conn->params.peer->srx.transport;
  37         msg.msg_namelen = conn->params.peer->srx.transport_len;
  38         msg.msg_control = NULL;
  39         msg.msg_controllen = 0;
  40         msg.msg_flags = 0;
  41
  42         /* send the packet with the don't fragment bit set if we currently
  43          * think it's small enough */
  44         if (skb->len - sizeof(struct rxrpc_wire_header) < conn->params.peer->maxdata) {
  45                 down_read(&conn->params.local->defrag_sem);
  46                 /* send the packet by UDP
  47                  * - returns -EMSGSIZE if UDP would have to fragment the packet
  48                  *   to go out of the interface
  49                  *   - in which case, we'll have processed the ICMP error
  50                  *     message and update the peer record
  51                  */
  52                 ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 1,
  53                                      iov[0].iov_len);
  54
  55                 up_read(&conn->params.local->defrag_sem);
  56                 if (ret == -EMSGSIZE)
  57                         goto send_fragmentable;
  58
  59                 _leave(" = %d [%u]", ret, conn->params.peer->maxdata);
  60                 return ret;
  61         }
  62
  63 send_fragmentable:
  64         /* attempt to send this message with fragmentation enabled */
  65         _debug("send fragment");
  66
  67         down_write(&conn->params.local->defrag_sem);
  68
  69         switch (conn->params.local->srx.transport.family) {
  70         case AF_INET:
  71                 opt = IP_PMTUDISC_DONT;
  72                 ret = kernel_setsockopt(conn->params.local->socket,
  73                                         SOL_IP, IP_MTU_DISCOVER,
  74                                         (char *)&opt, sizeof(opt));
  75                 if (ret == 0) {
  76                         ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 1,
  77                                              iov[0].iov_len);
  78
  79                         opt = IP_PMTUDISC_DO;
  80                         kernel_setsockopt(conn->params.local->socket, SOL_IP,
  81                                           IP_MTU_DISCOVER,
  82                                           (char *)&opt, sizeof(opt));
  83                 }
  84                 break;
  85         }
  86
  87         up_write(&conn->params.local->defrag_sem);
  88         _leave(" = %d [frag %u]", ret, conn->params.peer->maxdata);
  89         return ret;
  90 }