I am planning on adding this element to click. If anyone has any
comments/feedback on it, let me know.
Cliff
From 1e1a52e7aa6aa08e362210ba705bac7ca0d5e134 Mon Sep 17 00:00:00 2001
From: Cliff Frey <cl...@meraki.com>
Date: Wed, 29 Sep 2010 15:55:10 -0700
Subject: [PATCH] add TCPFragmenter element
This splits large TCP datagrams into smaller ones, it is useful for
testing tcp stream processing.
---
elements/tcpudp/tcpfragmenter.cc | 111 ++++++++++++++++++++++++++++++++++++++
elements/tcpudp/tcpfragmenter.hh | 45 +++++++++++++++
2 files changed, 156 insertions(+), 0 deletions(-)
create mode 100644 elements/tcpudp/tcpfragmenter.cc
create mode 100644 elements/tcpudp/tcpfragmenter.hh
diff --git a/elements/tcpudp/tcpfragmenter.cc b/elements/tcpudp/tcpfragmenter.cc
new file mode 100644
index 0000000..d15d1da
--- /dev/null
+++ b/elements/tcpudp/tcpfragmenter.cc
@@ -0,0 +1,111 @@
+/*
+ * tcpipencap.{cc,hh} -- element encapsulates packet in TCP/IP header
+ * Cliff Frey
+ *
+ * Copyright (c) 2010 Meraki, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, subject to the conditions
+ * listed in the Click LICENSE file. These conditions include: you must
+ * preserve this copyright notice, and you cannot mention the copyright
+ * holders in advertising related to the Software without their permission.
+ * The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
+ * notice is a summary of the Click LICENSE file; the license in that file is
+ * legally binding.
+ */
+
+#include <click/config.h>
+#include <clicknet/ip.h>
+#include <clicknet/tcp.h>
+#include "tcpfragmenter.hh"
+#include <click/confparse.hh>
+#include <click/error.hh>
+#include <click/glue.hh>
+#include <click/standard/alignmentinfo.hh>
+#ifdef CLICK_LINUXMODULE
+# include <net/checksum.h>
+#endif
+CLICK_DECLS
+
+TCPFragmenter::TCPFragmenter()
+{
+}
+
+TCPFragmenter::~TCPFragmenter()
+{
+}
+
+int
+TCPFragmenter::configure(Vector<String> &conf, ErrorHandler *errh)
+{
+ uint16_t mtu;
+ if (cp_va_kparse(conf, this, errh,
+ "MTU", cpkP+cpkM, cpUnsignedShort, &mtu,
+ cpEnd) < 0)
+ return -1;
+
+ if (mtu == 0)
+ return errh->error("MTU cannot be 0");
+
+ _mtu = mtu;
+
+ return 0;
+}
+
+void
+TCPFragmenter::push(int, Packet *p)
+{
+ int32_t tcp_len;
+ {
+ const click_ip *ip = reinterpret_cast<const click_ip *>(p->network_header());
+ const click_tcp *tcp = reinterpret_cast<const click_tcp *>(ip + 1);
+ tcp_len = (ntohs(ip->ip_len)-(ip->ip_hl<<2)-(tcp->th_off<<2));
+
+ if (!_mtu || tcp_len < _mtu) {
+ output(0).push(p);
+ return;
+ }
+ }
+
+ for (int offset = 0; offset < tcp_len; offset += _mtu) {
+ Packet *p_clone;
+ if (offset + _mtu < tcp_len)
+ p_clone = p->clone();
+ else {
+ p_clone = p;
+ p = 0;
+ }
+ if (!p_clone)
+ break;
+ WritablePacket *q = p_clone->uniqueify();
+ p_clone = 0;
+ click_ip *ip = reinterpret_cast<click_ip *>(q->network_header());
+ click_tcp *tcp = reinterpret_cast<click_tcp *>(ip + 1);
+ uint8_t *tcp_data = ((uint8_t *)tcp) + (tcp->th_off<<2);
+ int this_len = tcp_len - offset > _mtu ? _mtu : tcp_len - offset;
+ if (offset != 0)
+ memcpy(tcp_data, tcp_data + offset, this_len);
+ q->take(tcp_len - this_len);
+ ip->ip_len = htons(q->end_data() - q->network_header());
+ ip->ip_sum = 0;
+#if HAVE_FAST_CHECKSUM
+ ip->ip_sum = ip_fast_csum((unsigned char *)ip, sizeof(click_ip) >> 2);
+#else
+ ip->ip_sum = click_in_cksum((unsigned char *)ip, sizeof(click_ip));
+#endif
+
+ tcp->th_seq = htonl(ntohl(tcp->th_seq) + offset);
+ tcp->th_sum = 0;
+
+ // now calculate tcp header cksum
+ int plen = q->end_data() - (uint8_t*)tcp;
+ unsigned csum = click_in_cksum((unsigned char *)tcp, plen);
+ tcp->th_sum = click_in_cksum_pseudohdr(csum, ip, plen);
+ output(0).push(q);
+ }
+}
+
+CLICK_ENDDECLS
+EXPORT_ELEMENT(TCPFragmenter)
+ELEMENT_MT_SAFE(TCPFragmenter)
diff --git a/elements/tcpudp/tcpfragmenter.hh b/elements/tcpudp/tcpfragmenter.hh
new file mode 100644
index 0000000..f9b1feb
--- /dev/null
+++ b/elements/tcpudp/tcpfragmenter.hh
@@ -0,0 +1,45 @@
+#ifndef CLICK_TCPFRAGMENTER_HH
+#define CLICK_TCPFRAGMENTER_HH
+#include <click/element.hh>
+CLICK_DECLS
+
+/*
+=c
+
+TCPFragmenter(MTU)
+
+=s tcp
+
+fragments TCP packets to a maximum TCP payload size
+
+=d
+
+TCP Packets with payload length greater than the MTU are fragmented into
+multiple packets each containing at most MTU bytes of TCP payload. Each of
+these new packets will be a copy of the input packet except for checksums (ip
+and tcp), length (ip length), and tcp sequence number (for all fragments except
+the first).
+
+=a IPFragmenter, TCPIPEncap
+*/
+
+class TCPFragmenter : public Element { public:
+
+ TCPFragmenter();
+ ~TCPFragmenter();
+
+ const char *class_name() const { return "TCPFragmenter"; }
+ const char *port_count() const { return PORTS_1_1; }
+ const char *processing() const { return PUSH; }
+ bool can_live_reconfigure() const { return true; }
+
+ int configure(Vector<String> &, ErrorHandler *);
+
+ void push(int, Packet *);
+
+ private:
+ uint16_t _mtu;
+};
+
+CLICK_ENDDECLS
+#endif
--
1.7.3
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