Bugfix: read/write 16 and 32-bit values manually to avoid alignment issues.
This commit is contained in:
Darell Tan
parent
f1f39e0caa
commit
e0bf7227b1
98
mdns.c
98
mdns.c
@ -500,6 +500,32 @@ void rr_group_destroy(struct rr_group *group) {
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}
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}
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uint8_t *mdns_write_u16(uint8_t *ptr, const uint16_t v) {
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*ptr++ = (uint8_t) (v >> 8) & 0xFF;
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*ptr++ = (uint8_t) (v >> 0) & 0xFF;
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return ptr;
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}
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uint8_t *mdns_write_u32(uint8_t *ptr, const uint32_t v) {
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*ptr++ = (uint8_t) (v >> 24) & 0xFF;
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*ptr++ = (uint8_t) (v >> 16) & 0xFF;
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*ptr++ = (uint8_t) (v >> 8) & 0xFF;
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*ptr++ = (uint8_t) (v >> 0) & 0xFF;
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return ptr;
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}
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uint16_t mdns_read_u16(const uint8_t *ptr) {
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return ((ptr[0] & 0xFF) << 8) |
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((ptr[1] & 0xFF) << 0);
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}
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uint32_t mdns_read_u32(const uint8_t *ptr) {
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return ((ptr[0] & 0xFF) << 24) |
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((ptr[1] & 0xFF) << 16) |
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((ptr[2] & 0xFF) << 8) |
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((ptr[3] & 0xFF) << 0);
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}
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// initialize the packet for reply
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// clears the packet of list structures but not its list items
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void mdns_init_reply(struct mdns_pkt *pkt, uint16_t id) {
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@ -553,11 +579,11 @@ static size_t mdns_parse_qn(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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p += label_len(pkt_buf, pkt_len, off);
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rr->name = name;
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rr->type = ntohs( * (uint16_t *) p );
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rr->type = mdns_read_u16(p);
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p += sizeof(uint16_t);
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rr->unicast_query = (*p & 0x80) == 0x80;
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rr->rr_class = ntohs( * (uint16_t *) p) & ~0x80;
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rr->rr_class = mdns_read_u16(p) & ~0x80;
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p += sizeof(uint16_t);
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rr_list_append(&pkt->rr_qn, rr);
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@ -589,18 +615,18 @@ static size_t mdns_parse_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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p += label_len(pkt_buf, pkt_len, off);
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rr->name = name;
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rr->type = ntohs( * (uint16_t *) p );
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rr->type = mdns_read_u16(p);
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p += sizeof(uint16_t);
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rr->cache_flush = (*p & 0x80) == 0x80;
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rr->rr_class = ntohs( * (uint16_t *) p) & ~0x80;
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rr->rr_class = mdns_read_u16(p) & ~0x80;
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p += sizeof(uint16_t);
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rr->ttl = ntohl( * (uint32_t *) p );
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rr->ttl = mdns_read_u32(p);
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p += sizeof(uint32_t);
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// RR data
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rr_data_len = ntohs( * (uint16_t *) p );
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rr_data_len = mdns_read_u16(p);
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p += sizeof(uint16_t);
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if (p + rr_data_len > e) {
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@ -619,7 +645,7 @@ static size_t mdns_parse_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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parse_error = 1;
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break;
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}
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rr->data.A.addr = ntohl( * (uint32_t *) p );
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rr->data.A.addr = ntohl(mdns_read_u32(p)); /* addr already in net order */
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p += sizeof(uint32_t);
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break;
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@ -680,7 +706,7 @@ static size_t mdns_parse_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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// parse a MDNS packet into an mdns_pkt struct
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struct mdns_pkt *mdns_parse_pkt(uint8_t *pkt_buf, size_t pkt_len) {
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uint16_t *p = (uint16_t *) pkt_buf;
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uint8_t *p = pkt_buf;
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size_t off;
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struct mdns_pkt *pkt;
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int i;
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@ -691,14 +717,14 @@ struct mdns_pkt *mdns_parse_pkt(uint8_t *pkt_buf, size_t pkt_len) {
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MALLOC_ZERO_STRUCT(pkt, mdns_pkt);
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// parse header
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pkt->id = ntohs(*p); p++;
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pkt->flags = ntohs(*p); p++;
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pkt->num_qn = ntohs(*p); p++;
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pkt->num_ans_rr = ntohs(*p); p++;
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pkt->num_auth_rr = ntohs(*p); p++;
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pkt->num_add_rr = ntohs(*p); p++;
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pkt->id = mdns_read_u16(p); p += sizeof(uint16_t);
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pkt->flags = mdns_read_u16(p); p += sizeof(uint16_t);
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pkt->num_qn = mdns_read_u16(p); p += sizeof(uint16_t);
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pkt->num_ans_rr = mdns_read_u16(p); p += sizeof(uint16_t);
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pkt->num_auth_rr = mdns_read_u16(p); p += sizeof(uint16_t);
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pkt->num_add_rr = mdns_read_u16(p); p += sizeof(uint16_t);
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off = (uint8_t *) p - pkt_buf;
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off = p - pkt_buf;
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// parse questions
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for (i = 0; i < pkt->num_qn; i++) {
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@ -742,7 +768,7 @@ static size_t mdns_encode_name(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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// find match for compression
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for (c = comp; c; c = c->next) {
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if (cmp_nlabel(name, c->label) == 0) {
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*(uint16_t *) p = htons(0xC000 | (c->pos & ~0xC000));
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mdns_write_u16(p, 0xC000 | (c->pos & ~0xC000));
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return len + sizeof(uint16_t);
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}
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@ -792,16 +818,13 @@ static size_t mdns_encode_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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p += l;
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// type
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*(uint16_t *) p = htons(rr->type);
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p += sizeof(uint16_t);
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p = mdns_write_u16(p, rr->type);
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// class & cache flush
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*(uint16_t *) p = htons((rr->rr_class & ~0x8000) | (rr->cache_flush << 15));
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p += sizeof(uint16_t);
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p = mdns_write_u16(p, (rr->rr_class & ~0x8000) | (rr->cache_flush << 15));
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// TTL
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*(uint32_t *) p = htonl(rr->ttl);
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p += sizeof(uint32_t);
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p = mdns_write_u32(p, rr->ttl);
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// data length (filled in later)
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p += sizeof(uint16_t);
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@ -811,8 +834,8 @@ static size_t mdns_encode_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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switch (rr->type) {
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case RR_A:
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*(uint32_t *) p = (rr->data.A.addr);
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p += sizeof(uint32_t);
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/* htonl() needed coz addr already in net order */
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p = mdns_write_u32(p, htonl(rr->data.A.addr));
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break;
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case RR_PTR:
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@ -832,14 +855,11 @@ static size_t mdns_encode_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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break;
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case RR_SRV:
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*(uint16_t *) p = htons(rr->data.SRV.priority);
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p += sizeof(uint16_t);
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p = mdns_write_u16(p, rr->data.SRV.priority);
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*(uint16_t *) p = htons(rr->data.SRV.weight);
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p += sizeof(uint16_t);
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p = mdns_write_u16(p, rr->data.SRV.weight);
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*(uint16_t *) p = htons(rr->data.SRV.port);
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p += sizeof(uint16_t);
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p = mdns_write_u16(p, rr->data.SRV.port);
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p += mdns_encode_name(pkt_buf, pkt_len, p - pkt_buf,
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rr->data.SRV.target, comp);
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@ -866,7 +886,7 @@ static size_t mdns_encode_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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l = p - p_data;
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// fill in the length
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*(uint16_t *) (p - l - sizeof(uint16_t)) = htons(l);
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mdns_write_u16(p - l - sizeof(uint16_t), l);
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return p - pkt_buf - off;
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}
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@ -875,7 +895,7 @@ static size_t mdns_encode_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off,
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// returns the size of the entire MDNS packet
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size_t mdns_encode_pkt(struct mdns_pkt *answer, uint8_t *pkt_buf, size_t pkt_len) {
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struct name_comp *comp;
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uint16_t *p = (uint16_t *) pkt_buf;
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uint8_t *p = pkt_buf;
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//uint8_t *e = pkt_buf + pkt_len;
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size_t off;
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int i;
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@ -889,14 +909,14 @@ size_t mdns_encode_pkt(struct mdns_pkt *answer, uint8_t *pkt_buf, size_t pkt_len
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// this is an Answer - number of qns should be zero
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assert(answer->num_qn == 0);
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*p++ = htons(answer->id);
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*p++ = htons(answer->flags);
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*p++ = htons(answer->num_qn);
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*p++ = htons(answer->num_ans_rr);
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*p++ = htons(answer->num_auth_rr);
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*p++ = htons(answer->num_add_rr);
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p = mdns_write_u16(p, answer->id);
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p = mdns_write_u16(p, answer->flags);
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p = mdns_write_u16(p, answer->num_qn);
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p = mdns_write_u16(p, answer->num_ans_rr);
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p = mdns_write_u16(p, answer->num_auth_rr);
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p = mdns_write_u16(p, answer->num_add_rr);
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off = (uint8_t *) p - pkt_buf;
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off = p - pkt_buf;
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// allocate list for name compression
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comp = malloc(sizeof(struct name_comp));
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