diff options
| -rw-r--r-- | net/net.c | 188 |
1 files changed, 183 insertions, 5 deletions
@@ -1107,6 +1107,176 @@ static void CDPStart(void) } #endif +#ifdef CONFIG_IP_DEFRAG +/* + * This function collects fragments in a single packet, according + * to the algorithm in RFC815. It returns NULL or the pointer to + * a complete packet, in static storage + */ +#ifndef CONFIG_NET_MAXDEFRAG +#define CONFIG_NET_MAXDEFRAG 16384 +#endif +/* + * MAXDEFRAG, above, is chosen in the config file and is real data + * so we need to add the NFS overhead, which is more than TFTP. + * To use sizeof in the internal unnamed structures, we need a real + * instance (can't do "sizeof(struct rpc_t.u.reply))", unfortunately). + * The compiler doesn't complain nor allocates the actual structure + */ +static struct rpc_t rpc_specimen; +#define IP_PKTSIZE (CONFIG_NET_MAXDEFRAG + sizeof(rpc_specimen.u.reply)) + +#define IP_MAXUDP (IP_PKTSIZE - IP_HDR_SIZE_NO_UDP) + +/* + * this is the packet being assembled, either data or frag control. + * Fragments go by 8 bytes, so this union must be 8 bytes long + */ +struct hole { + /* first_byte is address of this structure */ + u16 last_byte; /* last byte in this hole + 1 (begin of next hole) */ + u16 next_hole; /* index of next (in 8-b blocks), 0 == none */ + u16 prev_hole; /* index of prev, 0 == none */ + u16 unused; +}; + +static IP_t *__NetDefragment(IP_t *ip, int *lenp) +{ + static uchar pkt_buff[IP_PKTSIZE] __attribute__((aligned(PKTALIGN))); + static u16 first_hole, total_len; + struct hole *payload, *thisfrag, *h, *newh; + IP_t *localip = (IP_t *)pkt_buff; + uchar *indata = (uchar *)ip; + int offset8, start, len, done = 0; + u16 ip_off = ntohs(ip->ip_off); + + /* payload starts after IP header, this fragment is in there */ + payload = (struct hole *)(pkt_buff + IP_HDR_SIZE_NO_UDP); + offset8 = (ip_off & IP_OFFS); + thisfrag = payload + offset8; + start = offset8 * 8; + len = ntohs(ip->ip_len) - IP_HDR_SIZE_NO_UDP; + + if (start + len > IP_MAXUDP) /* fragment extends too far */ + return NULL; + + if (!total_len || localip->ip_id != ip->ip_id) { + /* new (or different) packet, reset structs */ + total_len = 0xffff; + payload[0].last_byte = ~0; + payload[0].next_hole = 0; + payload[0].prev_hole = 0; + first_hole = 0; + /* any IP header will work, copy the first we received */ + memcpy(localip, ip, IP_HDR_SIZE_NO_UDP); + } + + /* + * What follows is the reassembly algorithm. We use the payload + * array as a linked list of hole descriptors, as each hole starts + * at a multiple of 8 bytes. However, last byte can be whatever value, + * so it is represented as byte count, not as 8-byte blocks. + */ + + h = payload + first_hole; + while (h->last_byte < start) { + if (!h->next_hole) { + /* no hole that far away */ + return NULL; + } + h = payload + h->next_hole; + } + + if (offset8 + (len / 8) <= h - payload) { + /* no overlap with holes (dup fragment?) */ + return NULL; + } + + if (!(ip_off & IP_FLAGS_MFRAG)) { + /* no more fragmentss: truncate this (last) hole */ + total_len = start + len; + h->last_byte = start + len; + } + + /* + * There is some overlap: fix the hole list. This code doesn't + * deal with a fragment that overlaps with two different holes + * (thus being a superset of a previously-received fragment). + */ + + if ( (h >= thisfrag) && (h->last_byte <= start + len) ) { + /* complete overlap with hole: remove hole */ + if (!h->prev_hole && !h->next_hole) { + /* last remaining hole */ + done = 1; + } else if (!h->prev_hole) { + /* first hole */ + first_hole = h->next_hole; + payload[h->next_hole].prev_hole = 0; + } else if (!h->next_hole) { + /* last hole */ + payload[h->prev_hole].next_hole = 0; + } else { + /* in the middle of the list */ + payload[h->next_hole].prev_hole = h->prev_hole; + payload[h->prev_hole].next_hole = h->next_hole; + } + + } else if (h->last_byte <= start + len) { + /* overlaps with final part of the hole: shorten this hole */ + h->last_byte = start; + + } else if (h >= thisfrag) { + /* overlaps with initial part of the hole: move this hole */ + newh = thisfrag + (len / 8); + *newh = *h; + h = newh; + if (h->next_hole) + payload[h->next_hole].prev_hole = (h - payload); + if (h->prev_hole) + payload[h->prev_hole].next_hole = (h - payload); + else + first_hole = (h - payload); + + } else { + /* fragment sits in the middle: split the hole */ + newh = thisfrag + (len / 8); + *newh = *h; + h->last_byte = start; + h->next_hole = (newh - payload); + newh->prev_hole = (h - payload); + if (newh->next_hole) + payload[newh->next_hole].prev_hole = (newh - payload); + } + + /* finally copy this fragment and possibly return whole packet */ + memcpy((uchar *)thisfrag, indata + IP_HDR_SIZE_NO_UDP, len); + if (!done) + return NULL; + + localip->ip_len = htons(total_len); + *lenp = total_len + IP_HDR_SIZE_NO_UDP; + return localip; +} + +static inline IP_t *NetDefragment(IP_t *ip, int *lenp) +{ + u16 ip_off = ntohs(ip->ip_off); + if (!(ip_off & (IP_OFFS | IP_FLAGS_MFRAG))) + return ip; /* not a fragment */ + return __NetDefragment(ip, lenp); +} + +#else /* !CONFIG_IP_DEFRAG */ + +static inline IP_t *NetDefragment(IP_t *ip, int *lenp) +{ + u16 ip_off = ntohs(ip->ip_off); + if (!(ip_off & (IP_OFFS | IP_FLAGS_MFRAG))) + return ip; /* not a fragment */ + return NULL; +} +#endif void NetReceive(volatile uchar * inpkt, int len) @@ -1333,10 +1503,12 @@ NetReceive(volatile uchar * inpkt, int len) case PROT_IP: debug("Got IP\n"); + /* Before we start poking the header, make sure it is there */ if (len < IP_HDR_SIZE) { debug("len bad %d < %lu\n", len, (ulong)IP_HDR_SIZE); return; } + /* Check the packet length */ if (len < ntohs(ip->ip_len)) { printf("len bad %d < %d\n", len, ntohs(ip->ip_len)); return; @@ -1344,21 +1516,20 @@ NetReceive(volatile uchar * inpkt, int len) len = ntohs(ip->ip_len); debug("len=%d, v=%02x\n", len, ip->ip_hl_v & 0xff); + /* Can't deal with anything except IPv4 */ if ((ip->ip_hl_v & 0xf0) != 0x40) { return; } - /* Can't deal with fragments */ - if (ip->ip_off & htons(IP_OFFS | IP_FLAGS_MFRAG)) { - return; - } - /* can't deal with headers > 20 bytes */ + /* Can't deal with IP options (headers != 20 bytes) */ if ((ip->ip_hl_v & 0x0f) > 0x05) { return; } + /* Check the Checksum of the header */ if (!NetCksumOk((uchar *)ip, IP_HDR_SIZE_NO_UDP / 2)) { puts ("checksum bad\n"); return; } + /* If it is not for us, ignore it */ tmp = NetReadIP(&ip->ip_dst); if (NetOurIP && tmp != NetOurIP && tmp != 0xFFFFFFFF) { #ifdef CONFIG_MCAST_TFTP @@ -1367,6 +1538,13 @@ NetReceive(volatile uchar * inpkt, int len) return; } /* + * The function returns the unchanged packet if it's not + * a fragment, and either the complete packet or NULL if + * it is a fragment (if !CONFIG_IP_DEFRAG, it returns NULL) + */ + if (!(ip = NetDefragment(ip, &len))) + return; + /* * watch for ICMP host redirects * * There is no real handler code (yet). We just watch |