ip_packet: Allow creation of IP packets from data
This commit is contained in:
Tobias Brunner
parent
b557f4a7cd
commit
d56d9a45d4
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@ -254,3 +254,154 @@ failed:
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chunk_free(&packet);
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return NULL;
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}
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/**
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* Calculate the checksum for the pseudo IP header
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*/
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static u_int16_t pseudo_header_checksum(host_t *src, host_t *dst,
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u_int8_t proto, chunk_t payload)
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{
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switch (src->get_family(src))
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{
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case AF_INET:
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{
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struct __attribute__((packed)) {
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u_int32_t src;
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u_int32_t dst;
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u_char zero;
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u_char proto;
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u_int16_t len;
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} pseudo = {
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.proto = proto,
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.len = htons(payload.len),
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};
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memcpy(&pseudo.src, src->get_address(src).ptr,
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sizeof(pseudo.src));
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memcpy(&pseudo.dst, dst->get_address(dst).ptr,
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sizeof(pseudo.dst));
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return chunk_internet_checksum(chunk_from_thing(pseudo));
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}
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case AF_INET6:
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{
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struct __attribute__((packed)) {
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u_char src[16];
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u_char dst[16];
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u_int32_t len;
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u_char zero[3];
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u_char next_header;
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} pseudo = {
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.next_header = proto,
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.len = htons(payload.len),
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};
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memcpy(&pseudo.src, src->get_address(src).ptr,
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sizeof(pseudo.src));
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memcpy(&pseudo.dst, dst->get_address(dst).ptr,
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sizeof(pseudo.dst));
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return chunk_internet_checksum(chunk_from_thing(pseudo));
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}
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}
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return 0xffff;
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}
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/**
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* Calculate transport header checksums
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*/
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static void fix_transport_checksum(host_t *src, host_t *dst, u_int8_t proto,
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chunk_t payload)
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{
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u_int16_t sum = 0;
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switch (proto)
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{
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case IPPROTO_UDP:
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{
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struct udphdr *udp;
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if (payload.len < sizeof(*udp))
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{
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return;
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}
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udp = (struct udphdr*)payload.ptr;
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udp->check = 0;
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sum = pseudo_header_checksum(src, dst, proto, payload);
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udp->check = chunk_internet_checksum_inc(payload, sum);
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break;
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}
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case IPPROTO_TCP:
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{
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struct tcphdr *tcp;
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if (payload.len < sizeof(*tcp))
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{
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return;
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}
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tcp = (struct tcphdr*)payload.ptr;
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tcp->check = 0;
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sum = pseudo_header_checksum(src, dst, proto, payload);
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tcp->check = chunk_internet_checksum_inc(payload, sum);
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break;
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}
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default:
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break;
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}
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}
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/**
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* Described in header.
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*/
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ip_packet_t *ip_packet_create_from_data(host_t *src, host_t *dst,
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u_int8_t next_header, chunk_t data)
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{
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chunk_t packet;
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int family;
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family = src->get_family(src);
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if (family != dst->get_family(dst))
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{
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DBG1(DBG_ESP, "address family does not match");
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return NULL;
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}
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switch (family)
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{
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case AF_INET:
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{
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struct ip ip = {
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.ip_v = 4,
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.ip_hl = 5,
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.ip_len = htons(20 + data.len),
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.ip_ttl = 0x80,
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.ip_p = next_header,
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};
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memcpy(&ip.ip_src, src->get_address(src).ptr, sizeof(ip.ip_src));
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memcpy(&ip.ip_dst, dst->get_address(dst).ptr, sizeof(ip.ip_dst));
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ip.ip_sum = chunk_internet_checksum(chunk_from_thing(ip));
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packet = chunk_cat("cc", chunk_from_thing(ip), data);
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fix_transport_checksum(src, dst, next_header,
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chunk_skip(packet, 20));
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return ip_packet_create(packet);
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}
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#ifdef HAVE_NETINET_IP6_H
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case AF_INET6:
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{
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struct ip6_hdr ip = {
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.ip6_flow = htonl(6),
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.ip6_plen = htons(40 + data.len),
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.ip6_nxt = next_header,
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.ip6_hlim = 0x80,
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};
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memcpy(&ip.ip6_src, src->get_address(src).ptr, sizeof(ip.ip6_src));
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memcpy(&ip.ip6_dst, dst->get_address(dst).ptr, sizeof(ip.ip6_dst));
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packet = chunk_cat("cc", chunk_from_thing(ip), data);
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fix_transport_checksum(src, dst, next_header,
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chunk_skip(packet, 40));
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return ip_packet_create(packet);
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}
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#endif /* HAVE_NETINET_IP6_H */
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default:
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DBG1(DBG_ESP, "unsupported address family");
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return NULL;
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}
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}
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@ -1,5 +1,5 @@
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/*
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* Copyright (C) 2012 Tobias Brunner
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* Copyright (C) 2012-2014 Tobias Brunner
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* Hochschule fuer Technik Rapperswil
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*
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* This program is free software; you can redistribute it and/or modify it
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@ -93,4 +93,16 @@ struct ip_packet_t {
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*/
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ip_packet_t *ip_packet_create(chunk_t packet);
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/**
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* Encode an IP packet from the given data.
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*
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* @param src source address (cloned)
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* @param dst destination address (cloned)
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* @param next_header the protocol (IPv4) or next header (IPv6)
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* @param data complete data after basic IP header (cloned)
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* @return ip_packet_t instance, or NULL if invalid
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*/
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ip_packet_t *ip_packet_create_from_data(host_t *src, host_t *dst,
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u_int8_t next_header, chunk_t data);
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#endif /** IP_PACKET_H_ @}*/
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