diff options
Diffstat (limited to 'translate.c')
| -rw-r--r-- | translate.c | 49 |
1 files changed, 17 insertions, 32 deletions
diff --git a/translate.c b/translate.c index 9a0f1b5..00ea0b9 100644 --- a/translate.c +++ b/translate.c @@ -208,10 +208,12 @@ int icmp_to_icmp6(clat_packet out, int pos, const struct icmphdr *icmp, uint32_t // The pseudo-header checksum was calculated on the transport length of the original IPv4 // packet that we were asked to translate. This transport length is 20 bytes smaller than it // needs to be, because the ICMP error contains an IPv4 header, which we will be translating to - // an IPv6 header, which is 20 bytes longer. Fix it up here. + // an IPv6 header, which is 20 bytes longer. Fix it up here. This is simpler than the + // alternative, which is to always update the pseudo-header checksum in all UDP/TCP/ICMP + // translation functions (rather than pre-calculating it when translating the IPv4 header). // We only need to do this for ICMP->ICMPv6, not ICMPv6->ICMP, because ICMP does not use the // pseudo-header when calculating its checksum (as the IPv4 header has its own checksum). - checksum = checksum + htons(20); + checksum = htonl(ntohl(checksum) + 20); } else if (icmp6_type == ICMP6_ECHO_REQUEST || icmp6_type == ICMP6_ECHO_REPLY) { // Ping packet. icmp6_targ->icmp6_id = icmp->un.echo.id; @@ -296,12 +298,10 @@ int generic_packet(clat_packet out, int pos, const char *payload, size_t len) { * takes a udp packet and sets it up for translation * out - output packet * udp - pointer to udp header in packet - * old_sum - pseudo-header checksum of old header - * new_sum - pseudo-header checksum of new header + * checksum - pseudo-header checksum * len - size of ip payload */ -int udp_packet(clat_packet out, int pos, const struct udphdr *udp, - uint32_t old_sum, uint32_t new_sum, size_t len) { +int udp_packet(clat_packet out, int pos, const struct udphdr *udp, uint32_t checksum, size_t len) { const char *payload; size_t payload_size; @@ -313,7 +313,7 @@ int udp_packet(clat_packet out, int pos, const struct udphdr *udp, payload = (const char *) (udp + 1); payload_size = len - sizeof(struct udphdr); - return udp_translate(out, pos, udp, old_sum, new_sum, payload, payload_size); + return udp_translate(out, pos, udp, checksum, payload, payload_size); } /* function: tcp_packet @@ -324,8 +324,7 @@ int udp_packet(clat_packet out, int pos, const struct udphdr *udp, * len - size of ip payload * returns: the highest position in the output clat_packet that's filled in */ -int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp, - uint32_t old_sum, uint32_t new_sum, size_t len) { +int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp, uint32_t checksum, size_t len) { const char *payload; size_t payload_size, header_size; @@ -348,21 +347,20 @@ int tcp_packet(clat_packet out, int pos, const struct tcphdr *tcp, payload = ((const char *) tcp) + header_size; payload_size = len - header_size; - return tcp_translate(out, pos, tcp, header_size, old_sum, new_sum, payload, payload_size); + return tcp_translate(out, pos, tcp, header_size, checksum, payload, payload_size); } /* function: udp_translate * common between ipv4/ipv6 - setup checksum and send udp packet * out - output packet * udp - udp header - * old_sum - pseudo-header checksum of old header - * new_sum - pseudo-header checksum of new header + * checksum - pseudo-header checksum * payload - tcp payload * payload_size - size of payload * returns: the highest position in the output clat_packet that's filled in */ -int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t old_sum, - uint32_t new_sum, const char *payload, size_t payload_size) { +int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t checksum, + const char *payload, size_t payload_size) { struct udphdr *udp_targ = out[pos].iov_base; memcpy(udp_targ, udp, sizeof(struct udphdr)); @@ -371,22 +369,8 @@ int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t o out[CLAT_POS_PAYLOAD].iov_base = (char *) payload; out[CLAT_POS_PAYLOAD].iov_len = payload_size; - if (udp_targ->check) { - udp_targ->check = ip_checksum_adjust(udp->check, old_sum, new_sum); - } else { - // Zero checksums are special. RFC 768 says, "An all zero transmitted checksum value means that - // the transmitter generated no checksum (for debugging or for higher level protocols that - // don't care)." However, in IPv6 zero UDP checksums were only permitted by RFC 6935 (2013). So - // for safety we recompute it. - udp_targ->check = 0; // Checksum field must be 0 when calculating checksum. - udp_targ->check = packet_checksum(new_sum, out, pos); - } - - // RFC 768: "If the computed checksum is zero, it is transmitted as all ones (the equivalent - // in one's complement arithmetic)." - if (!udp_targ->check) { - udp_targ->check = 0xffff; - } + udp_targ->check = 0; // Checksum field must be 0 when calculating checksum. + udp_targ->check = packet_checksum(checksum, out, pos); return CLAT_POS_PAYLOAD + 1; } @@ -405,7 +389,7 @@ int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t o * TODO: hosts without pmtu discovery - non DF packets will rely on fragmentation (unimplemented) */ int tcp_translate(clat_packet out, int pos, const struct tcphdr *tcp, size_t header_size, - uint32_t old_sum, uint32_t new_sum, const char *payload, size_t payload_size) { + uint32_t checksum, const char *payload, size_t payload_size) { struct tcphdr *tcp_targ = out[pos].iov_base; out[pos].iov_len = header_size; @@ -422,7 +406,8 @@ int tcp_translate(clat_packet out, int pos, const struct tcphdr *tcp, size_t hea out[CLAT_POS_PAYLOAD].iov_base = (char *)payload; out[CLAT_POS_PAYLOAD].iov_len = payload_size; - tcp_targ->check = ip_checksum_adjust(tcp->check, old_sum, new_sum); + tcp_targ->check = 0; // Checksum field must be 0 when calculating checksum. + tcp_targ->check = packet_checksum(checksum, out, pos); return CLAT_POS_PAYLOAD + 1; } |