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When studying the Linux source code and Wireshark dumps it seems like the no_frag flag in the IPv4 header is always set. Following discussions in the Internet on this subject indicates that modern routers never fragment packets, and that it isn't even supported in many cases. Adding to this that incoming messages forwarded on the tap interface never even pass through a router it seems safe to always set this flag. This makes the IPv4 headers of forwarded messages identical to those sent by the external sockets, something we must consider desirable. Signed-off-by: Jon Maloy <jmaloy@redhat.com> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
108 lines
2.8 KiB
C
108 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later
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* Copyright (c) 2021 Red Hat GmbH
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* Author: Stefano Brivio <sbrivio@redhat.com>
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*/
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#ifndef IP_H
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#define IP_H
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#include <netinet/ip.h>
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#include <netinet/ip6.h>
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#define IN4_IS_ADDR_UNSPECIFIED(a) \
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(((struct in_addr *)(a))->s_addr == htonl_constant(INADDR_ANY))
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#define IN4_IS_ADDR_BROADCAST(a) \
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(((struct in_addr *)(a))->s_addr == htonl_constant(INADDR_BROADCAST))
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#define IN4_IS_ADDR_LOOPBACK(a) \
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(ntohl(((struct in_addr *)(a))->s_addr) >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET)
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#define IN4_IS_ADDR_MULTICAST(a) \
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(IN_MULTICAST(ntohl(((struct in_addr *)(a))->s_addr)))
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#define IN4_ARE_ADDR_EQUAL(a, b) \
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(((struct in_addr *)(a))->s_addr == ((struct in_addr *)b)->s_addr)
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#define IN4ADDR_LOOPBACK_INIT \
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{ .s_addr = htonl_constant(INADDR_LOOPBACK) }
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#define IN4ADDR_ANY_INIT \
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{ .s_addr = htonl_constant(INADDR_ANY) }
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#define IN4_IS_ADDR_LINKLOCAL(a) \
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((ntohl(((struct in_addr *)(a))->s_addr) >> 16) == 0xa9fe)
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#define IN4_IS_PREFIX_LINKLOCAL(a, len) \
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((len) >= 16 && IN4_IS_ADDR_LINKLOCAL(a))
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#define L2_BUF_IP4_INIT(proto) \
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{ \
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.version = 4, \
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.ihl = 5, \
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.tos = 0, \
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.tot_len = 0, \
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.id = 0, \
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.frag_off = htons(IP_DF), \
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.ttl = 0xff, \
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.protocol = (proto), \
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.saddr = 0, \
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.daddr = 0, \
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}
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#define L2_BUF_IP4_PSUM(proto) ((uint32_t)htons_constant(0x4500) + \
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(uint32_t)htons_constant(IP_DF) + \
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(uint32_t)htons(0xff00 | (proto)))
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#define IN6_IS_PREFIX_LINKLOCAL(a, len) \
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((len) >= 10 && IN6_IS_ADDR_LINKLOCAL(a))
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#define L2_BUF_IP6_INIT(proto) \
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{ \
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.priority = 0, \
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.version = 6, \
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.flow_lbl = { 0 }, \
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.payload_len = 0, \
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.nexthdr = (proto), \
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.hop_limit = 255, \
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.saddr = IN6ADDR_ANY_INIT, \
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.daddr = IN6ADDR_ANY_INIT, \
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}
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struct ipv6hdr {
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wpedantic"
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#if __BYTE_ORDER == __BIG_ENDIAN
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uint8_t version:4,
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priority:4;
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#else
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uint8_t priority:4,
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version:4;
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#endif
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#pragma GCC diagnostic pop
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uint8_t flow_lbl[3];
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uint16_t payload_len;
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uint8_t nexthdr;
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uint8_t hop_limit;
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struct in6_addr saddr;
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struct in6_addr daddr;
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};
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struct ipv6_opt_hdr {
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uint8_t nexthdr;
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uint8_t hdrlen;
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/*
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* TLV encoded option data follows.
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*/
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} __attribute__((packed)); /* required for some archs */
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char *ipv6_l4hdr(const struct pool *p, int idx, size_t offset, uint8_t *proto,
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size_t *dlen);
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/* IPv6 link-local all-nodes multicast adddress, ff02::1 */
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static const struct in6_addr in6addr_ll_all_nodes = {
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.s6_addr = {
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0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
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},
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};
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/* IPv4 Limited Broadcast (RFC 919, Section 7), 255.255.255.255 */
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static const struct in_addr in4addr_broadcast = { 0xffffffff };
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#endif /* IP_H */
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