diff options
Diffstat (limited to 'support/resolv_test.c')
| -rw-r--r-- | support/resolv_test.c | 294 |
1 files changed, 161 insertions, 133 deletions
diff --git a/support/resolv_test.c b/support/resolv_test.c index e968c83633..3f2a09f36f 100644 --- a/support/resolv_test.c +++ b/support/resolv_test.c @@ -43,15 +43,99 @@ enum max_response_length = 65536 }; -/* List of pointers to be freed. The hash table implementation - (struct hsearch_data) does not provide a way to deallocate all - objects, so this approach is used to avoid memory leaks. */ -struct to_be_freed +/* Used for locating domain names containing for the purpose of + forming compression references. */ +struct compressed_name { - struct to_be_freed *next; - void *ptr; + uint16_t offset; + unsigned char length; + unsigned char name[]; /* Without terminating NUL. */ }; +static struct compressed_name * +allocate_compressed_name (const unsigned char *encoded, unsigned int offset) +{ + /* Compute the length of the domain name. */ + size_t length; + { + const unsigned char *p; + for (p = encoded; *p != '\0';) + { + /* No compression references are allowed. */ + TEST_VERIFY (*p <= 63); + /* Skip over the label. */ + p += 1 + *p; + } + length = p - encoded; + ++length; /* For the terminating NUL byte. */ + } + TEST_VERIFY_EXIT (length <= 255); + + struct compressed_name *result + = xmalloc (offsetof (struct compressed_name, name) + length); + result->offset = offset; + result->length = length; + memcpy (result->name, encoded, length); + return result; +} + +/* Convert CH to lower case. Only change letters in the ASCII + range. */ +static inline unsigned char +ascii_tolower (unsigned char ch) +{ + if ('A' <= ch && ch <= 'Z') + return ch - 'A' + 'a'; + else + return ch; +} + +/* Compare both names, for use with tsearch. The order is arbitrary, + but the comparison is case-insenstive. */ +static int +compare_compressed_name (const void *left, const void *right) +{ + const struct compressed_name *crleft = left; + const struct compressed_name *crright = right; + + if (crleft->length != crright->length) + /* The operands are converted to int before the subtraction. */ + return crleft->length - crright->length; + + const unsigned char *nameleft = crleft->name; + const unsigned char *nameright = crright->name; + + while (true) + { + int lenleft = *nameleft++; + int lenright = *nameright++; + + /* Labels must not e compression references. */ + TEST_VERIFY (lenleft <= 63); + TEST_VERIFY (lenright <= 63); + + if (lenleft != lenright) + return left - right; + if (lenleft == 0) + /* End of name reached without spotting a difference. */ + return 0; + /* Compare the label in a case-insenstive manner. */ + const unsigned char *endnameleft = nameleft + lenleft; + while (nameleft < endnameleft) + { + int l = *nameleft++; + int r = *nameright++; + if (l != r) + { + l = ascii_tolower (l); + r = ascii_tolower (r); + if (l != r) + return l - r; + } + } + } +} + struct resolv_response_builder { const unsigned char *query_buffer; @@ -67,11 +151,8 @@ struct resolv_response_builder written RDATA sub-structure. 0 if no RDATA is being written. */ size_t current_rdata_offset; - /* Hash table for locating targets for label compression. */ - struct hsearch_data compression_offsets; - /* List of pointers which need to be freed. Used for domain names - involved in label compression. */ - struct to_be_freed *to_be_freed; + /* tsearch tree for locating targets for label compression. */ + void *compression_offsets; /* Must be last. Not zeroed for performance reasons. */ unsigned char buffer[max_response_length]; @@ -79,18 +160,6 @@ struct resolv_response_builder /* Response builder. */ -/* Add a pointer to the list of pointers to be freed when B is - deallocated. */ -static void -response_push_pointer_to_free (struct resolv_response_builder *b, void *ptr) -{ - if (ptr == NULL) - return; - struct to_be_freed *e = xmalloc (sizeof (*e)); - *e = (struct to_be_freed) {b->to_be_freed, ptr}; - b->to_be_freed = e; -} - void resolv_response_init (struct resolv_response_builder *b, struct resolv_response_flags flags) @@ -194,120 +263,88 @@ void resolv_response_add_name (struct resolv_response_builder *b, const char *const origname) { - /* Normalized name. */ - char *name; - /* Normalized name with case preserved. */ - char *name_case; - { - size_t namelen = strlen (origname); - /* Remove trailing dots. FIXME: Handle trailing quoted dots. */ - while (namelen > 0 && origname[namelen - 1] == '.') - --namelen; - name = xmalloc (namelen + 1); - name_case = xmalloc (namelen + 1); - /* Copy and convert to lowercase. FIXME: This needs to normalize - escaping as well. */ - for (size_t i = 0; i < namelen; ++i) - { - char ch = origname[i]; - name_case[i] = ch; - if ('A' <= ch && ch <= 'Z') - ch = ch - 'A' + 'a'; - name[i] = ch; - } - name[namelen] = 0; - name_case[namelen] = 0; - } - char *name_start = name; - char *name_case_start = name_case; + unsigned char encoded_name[NS_MAXDNAME]; + if (ns_name_pton (origname, encoded_name, sizeof (encoded_name)) < 0) + FAIL_EXIT1 ("ns_name_pton (\"%s\"): %m", origname); - bool compression = false; - while (*name) + /* Copy the encoded name into the output buffer, apply compression + where possible. */ + for (const unsigned char *name = encoded_name; ;) { - /* Search for a previous name we can reference. */ - ENTRY new_entry = + if (*name == '\0') { - .key = name, - .data = (void *) (uintptr_t) b->offset, - }; + /* We have reached the end of the name. Add the terminating + NUL byte. */ + response_add_byte (b, '\0'); + break; + } - /* If the label can be a compression target because it is at a - reachable offset, add it to the hash table. */ - ACTION action; - if (b->offset < (1 << 12)) - action = ENTER; - else - action = FIND; + /* Set to the compression target if compression is possible. */ + struct compressed_name *crname_target; - /* Search for known compression offsets in the hash table. */ - ENTRY *e; - if (hsearch_r (new_entry, action, &e, &b->compression_offsets) == 0) - { - if (action == FIND && errno == ESRCH) - /* Fall through. */ - e = NULL; - else - FAIL_EXIT1 ("hsearch_r failure in name compression: %m"); - } + /* Compression references can only reach the beginning of the + packet. */ + enum { compression_limit = 1 << 12 }; + + { + /* The trailing part of the name to be looked up in the tree + with the compression targets. */ + struct compressed_name *crname + = allocate_compressed_name (name, b->offset); + + if (b->offset < compression_limit) + { + /* Add the name to the tree, for future compression + references. */ + void **ptr = tsearch (crname, &b->compression_offsets, + compare_compressed_name); + if (ptr == NULL) + FAIL_EXIT1 ("tsearch out of memory"); + crname_target = *ptr; + + if (crname_target != crname) + /* The new name was not actually added to the tree. + Deallocate it. */ + free (crname); + else + /* Signal that the tree did not yet contain the name, + but keep the allocation because it is now part of the + tree. */ + crname_target = NULL; + } + else + { + /* This name cannot be reached by a compression reference. + No need to add it to the tree for future reference. */ + void **ptr = tfind (crname, &b->compression_offsets, + compare_compressed_name); + if (ptr != NULL) + crname_target = *ptr; + else + crname_target = NULL; + TEST_VERIFY (crname_target != crname); + /* Not added to the tree. */ + free (crname); + } + } - /* The name is known. Reference the previous location. */ - if (e != NULL && e->data != new_entry.data) + if (crname_target != NULL) { - size_t old_offset = (uintptr_t) e->data; + /* The name is known. Reference the previous location. */ + unsigned int old_offset = crname_target->offset; + TEST_VERIFY_EXIT (old_offset < compression_limit); response_add_byte (b, 0xC0 | (old_offset >> 8)); response_add_byte (b, old_offset); - compression = true; break; } - - /* The name does not exist yet. Write one label. First, add - room for the label length. */ - size_t buffer_label_offset = b->offset; - response_add_byte (b, 0); - - /* Copy the label. */ - while (true) + else { - char ch = *name_case; - if (ch == '\0') - break; - ++name; - ++name_case; - if (ch == '.') - break; - /* FIXME: Handle escaping. */ - response_add_byte (b, ch); + /* The name is new. Add this label. */ + unsigned int len = 1 + *name; + resolv_response_add_data (b, name, len); + name += len; } - - /* Patch in the label length. */ - size_t label_length = b->offset - buffer_label_offset - 1; - if (label_length == 0) - FAIL_EXIT1 ("empty label in name compression: %s", origname); - if (label_length > 63) - FAIL_EXIT1 ("label too long in name compression: %s", origname); - b->buffer[buffer_label_offset] = label_length; - - /* Continue with the tail of the name and the next label. */ - } - - if (compression) - { - /* If we found an immediate match for the name, we have not put - it into the hash table, and can free it immediately. */ - if (name == name_start) - free (name_start); - else - response_push_pointer_to_free (b, name_start); - } - else - { - /* Terminate the sequence of labels. With compression, this is - implicit in the compression reference. */ - response_add_byte (b, 0); - response_push_pointer_to_free (b, name_start); } - - free (name_case_start); } void @@ -403,22 +440,13 @@ response_builder_allocate memset (b, 0, offsetof (struct resolv_response_builder, buffer)); b->query_buffer = query_buffer; b->query_length = query_length; - TEST_VERIFY_EXIT (hcreate_r (10000, &b->compression_offsets) != 0); return b; } static void response_builder_free (struct resolv_response_builder *b) { - struct to_be_freed *current = b->to_be_freed; - while (current != NULL) - { - struct to_be_freed *next = current->next; - free (current->ptr); - free (current); - current = next; - } - hdestroy_r (&b->compression_offsets); + tdestroy (b->compression_offsets, free); free (b); } |