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dhcp: truncate packets instead of padding them to 574 bytes. closes bug 1849
function old new delta udhcp_send_raw_packet 411 456 +45 udhcp_send_kernel_packet 259 271 +12 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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@ -173,6 +173,7 @@ int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
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{
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{
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struct sockaddr_ll dest_sll;
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struct sockaddr_ll dest_sll;
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struct ip_udp_dhcp_packet packet;
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struct ip_udp_dhcp_packet packet;
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unsigned padding;
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int fd;
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int fd;
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int result = -1;
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int result = -1;
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const char *msg;
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const char *msg;
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@ -198,34 +199,40 @@ int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
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goto ret_close;
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goto ret_close;
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}
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}
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/* We were sending full-sized DHCP packets (zero padded),
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* but some badly configured servers were seen dropping them.
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* Apparently they drop all DHCP packets >576 *ethernet* octets big,
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* whereas they may only drop packets >576 *IP* octets big
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* (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
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*
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* In order to work with those buggy servers,
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* we truncate packets after end option byte.
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*/
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padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
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packet.ip.protocol = IPPROTO_UDP;
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packet.ip.protocol = IPPROTO_UDP;
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packet.ip.saddr = source_nip;
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packet.ip.saddr = source_nip;
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packet.ip.daddr = dest_nip;
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packet.ip.daddr = dest_nip;
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packet.udp.source = htons(source_port);
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packet.udp.source = htons(source_port);
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packet.udp.dest = htons(dest_port);
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packet.udp.dest = htons(dest_port);
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/* size, excluding IP header: */
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/* size, excluding IP header: */
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packet.udp.len = htons(UPD_DHCP_SIZE);
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packet.udp.len = htons(UPD_DHCP_SIZE - padding);
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/* for UDP checksumming, ip.len is set to UDP packet len */
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/* for UDP checksumming, ip.len is set to UDP packet len */
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packet.ip.tot_len = packet.udp.len;
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packet.ip.tot_len = packet.udp.len;
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packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
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packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE - padding);
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/* but for sending, it is set to IP packet len */
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/* but for sending, it is set to IP packet len */
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packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
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packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE - padding);
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packet.ip.ihl = sizeof(packet.ip) >> 2;
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packet.ip.ihl = sizeof(packet.ip) >> 2;
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packet.ip.version = IPVERSION;
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packet.ip.version = IPVERSION;
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packet.ip.ttl = IPDEFTTL;
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packet.ip.ttl = IPDEFTTL;
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packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
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packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
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/* Currently we send full-sized DHCP packets (zero padded).
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* If you need to change this: last byte of the packet is
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* packet.data.options[udhcp_end_option(packet.data.options)]
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*/
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udhcp_dump_packet(dhcp_pkt);
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udhcp_dump_packet(dhcp_pkt);
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result = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
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result = sendto(fd, &packet, IP_UPD_DHCP_SIZE - padding, /*flags:*/ 0,
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(struct sockaddr *) &dest_sll, sizeof(dest_sll));
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(struct sockaddr *) &dest_sll, sizeof(dest_sll));
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msg = "sendto";
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msg = "sendto";
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ret_close:
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ret_close:
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close(fd);
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close(fd);
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/* FIXME: and if result >= 0 but != IP_UPD_DHCP_SIZE? */
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if (result < 0) {
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if (result < 0) {
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ret_msg:
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ret_msg:
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bb_perror_msg(msg, "PACKET");
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bb_perror_msg(msg, "PACKET");
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@ -239,6 +246,7 @@ int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
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uint32_t dest_nip, int dest_port)
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uint32_t dest_nip, int dest_port)
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{
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{
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struct sockaddr_in client;
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struct sockaddr_in client;
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unsigned padding;
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int fd;
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int fd;
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int result = -1;
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int result = -1;
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const char *msg;
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const char *msg;
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@ -268,13 +276,13 @@ int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
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goto ret_close;
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goto ret_close;
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}
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}
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/* Currently we send full-sized DHCP packets (see above) */
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udhcp_dump_packet(dhcp_pkt);
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udhcp_dump_packet(dhcp_pkt);
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result = safe_write(fd, dhcp_pkt, DHCP_SIZE);
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padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
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result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
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msg = "write";
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msg = "write";
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ret_close:
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ret_close:
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close(fd);
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close(fd);
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/* FIXME: and if result >= 0 but != DHCP_SIZE? */
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if (result < 0) {
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if (result < 0) {
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ret_msg:
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ret_msg:
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bb_perror_msg(msg, "UDP");
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bb_perror_msg(msg, "UDP");
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