diff options
Diffstat (limited to 'src/nlmsg.c')
| -rw-r--r-- | src/nlmsg.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/src/nlmsg.c b/src/nlmsg.c index 4f5e503..b2e3853 100644 --- a/src/nlmsg.c +++ b/src/nlmsg.c @@ -8,6 +8,7 @@ */ #include <stdbool.h> #include <stdio.h> +#include <stdlib.h> #include <ctype.h> #include <errno.h> #include <string.h> @@ -371,5 +372,189 @@ mnl_nlmsg_fprintf(FILE *fd, const void *data, size_t datalen, } /** + * \defgroup batch Netlink message batch helpers + * + * This library provides helpers to batch several messages into one single + * datagram. These helpers do not perform strict memory boundary checkings. + * + * The following figure represents a Netlink message batch: + * + * |<-------------- MNL_SOCKET_BUFFER_SIZE ------------->| + * |<-------------------- batch ------------------>| | + * |-----------|-----------|-----------|-----------|-----------| + * |<- nlmsg ->|<- nlmsg ->|<- nlmsg ->|<- nlmsg ->|<- nlmsg ->| + * |-----------|-----------|-----------|-----------|-----------| + * ^ ^ + * | | + * message N message N+1 + * + * To start the batch, you have to call mnl_nlmsg_batch_start() and you can + * use mnl_nlmsg_batch_stop() to release it. + * + * You have to invoke mnl_nlmsg_batch_next() to get room for a new message + * in the batch. If this function returns NULL, it means that the last + * message that was added (message N+1 in the figure above) does not fit the + * batch. Thus, you have to send the batch (which includes until message N) + * and, then, you have to call mnl_nlmsg_batch_reset() to re-initialize + * the batch (this moves message N+1 to the head of the buffer). For that + * reason, the buffer that you have to use to store the batch must be double + * of MNL_SOCKET_BUFFER_SIZE to ensure that the last message (message N+1) + * that did not fit into the batch is written inside valid memory boundaries. + * + * @{ + */ + +struct mnl_nlmsg_batch { + /* the buffer that is used to store the batch. */ + void *buf; + size_t limit; + size_t buflen; + /* the current netlink message in the batch. */ + void *cur; + bool overflow; +}; + +/** + * mnl_nlmsg_batch_start - initialize a batch + * \param buf pointer to the buffer that will store this batch + * \param limit maximum size of the batch (should be MNL_SOCKET_BUFFER_SIZE). + * + * The buffer that you pass must be double of MNL_SOCKET_BUFFER_SIZE. The + * limit must be half of the buffer size, otherwise expect funny memory + * corruptions 8-). + * + * You can allocate the buffer that you use to store the batch in the stack or + * the heap, no restrictions in this regard. This function returns NULL on + * error. + */ +EXPORT_SYMBOL struct mnl_nlmsg_batch * +mnl_nlmsg_batch_start(void *buf, size_t limit) +{ + struct mnl_nlmsg_batch *b; + + b = malloc(sizeof(struct mnl_nlmsg_batch)); + if (b == NULL) + return NULL; + + b->buf = buf; + b->limit = limit; + b->buflen = 0; + b->cur = buf; + b->overflow = false; + + return b; +} + +/** + * mnl_nlmsg_batch_stop - release a batch + * \param b pointer to batch + * + * This function returns the amount of data that is part of this batch. + */ +EXPORT_SYMBOL void +mnl_nlmsg_batch_stop(struct mnl_nlmsg_batch *b) +{ + free(b); +} + +/** + * mnl_nlmsg_batch_next - get room for the next message in the batch + * \param b pointer to batch + * + * This function returns a pointer to the beginning of the new Netlink message + * in the batch. It returns false if the last message did not fit into the + * batch. + * + * You have to put at least one message in the batch before calling this + * function, otherwise your application is likely to crash. + */ +EXPORT_SYMBOL bool +mnl_nlmsg_batch_next(struct mnl_nlmsg_batch *b) +{ + struct nlmsghdr *nlh = b->cur; + + if (b->buflen + nlh->nlmsg_len > b->limit) { + b->overflow = true; + return false; + } + b->cur = b->buf + b->buflen + nlh->nlmsg_len; + b->buflen += nlh->nlmsg_len; + return true; +} + +/** + * mnl_nlmsg_batch_reset - reset the batch + * \param b pointer to batch + * + * This function allows to reset a batch, so you can reuse it to create a + * new one. This function moves the last message which does not fit the + * batch to the head of the buffer, if any. + */ +EXPORT_SYMBOL void +mnl_nlmsg_batch_reset(struct mnl_nlmsg_batch *b) +{ + if (b->overflow) { + struct nlmsghdr *nlh = b->cur; + memcpy(b->buf, b->cur, nlh->nlmsg_len); + b->buflen = nlh->nlmsg_len; + b->cur = b->buf + b->buflen; + b->overflow = false; + } else { + b->buflen = 0; + b->cur = b->buf; + } +} + +/** + * mnl_nlmsg_batch_size - get current size of the batch + * \param b pointer to batch + * + * This function returns the current size of the batch. + */ +EXPORT_SYMBOL size_t +mnl_nlmsg_batch_size(struct mnl_nlmsg_batch *b) +{ + return b->buflen; +} + +/** + * mnl_nlmsg_batch_head - get head of this batch + * \param b pointer to batch + * + * This function returns a pointer to the head of the batch, which is the + * beginning of the buffer that is used. + */ +EXPORT_SYMBOL void * +mnl_nlmsg_batch_head(struct mnl_nlmsg_batch *b) +{ + return b->buf; +} + +/** + * mnl_nlmsg_batch_current - returns current position in the batch + * \param b pointer to batch + * + * This function returns a pointer to the current position in the buffer + * that is used to store the batch. + */ +EXPORT_SYMBOL void * +mnl_nlmsg_batch_current(struct mnl_nlmsg_batch *b) +{ + return b->cur; +} + +/** + * mnl_nlmsg_batch_is_empty - check if there is any message in the batch + * \param b pointer to batch + * + * This function returns true if the batch is empty. + */ +EXPORT_SYMBOL bool +mnl_nlmsg_batch_is_empty(struct mnl_nlmsg_batch *b) +{ + return b->buflen == 0; +} + +/** * @} */ |