ipv4.h
/*
* Copyright (C) 2016-2017 Authors of Cilium
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef __LIB_IPV4__
#define __LIB_IPV4__
#include <linux/ip.h>
#include "dbg.h"
static inline int ipv4_load_daddr(struct __sk_buff *skb, int off, __u32 *dst)
{
return skb_load_bytes(skb, off + offsetof(struct iphdr, daddr), dst, 4);
}
static inline int ipv4_dec_ttl(struct __sk_buff *skb, int off, struct iphdr *ip4)
{
__u8 new_ttl, ttl = ip4->ttl;
if (ttl <= 1)
return 1;
new_ttl = ttl - 1;
/* l3_csum_replace() takes at min 2 bytes, zero extended. */
l3_csum_replace(skb, off + offsetof(struct iphdr, check), ttl, new_ttl, 2);
skb_store_bytes(skb, off + offsetof(struct iphdr, ttl), &new_ttl, sizeof(new_ttl), 0);
return 0;
}
static inline int ipv4_hdrlen(struct iphdr *ip4)
{
return ip4->ihl * 4;
}
static inline bool ipv4_is_fragment(struct iphdr *ip4)
{
// The frag_off portion of the header consists of:
//
// +----+----+----+----------------------------------+
// | RS | DF | MF | ...13 bits of fragment offset... |
// +----+----+----+----------------------------------+
//
// If "More fragments" or the offset is nonzero, then this is an IP
// fragment. The evil bit must be set to 0 (RFC791, RFC3514).
return ip4->frag_off & bpf_htons(0xBFFF);
}
#endif /* __LIB_IPV4__ */