diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/gsm/gsm0480.c | 88 | ||||
| -rw-r--r-- | src/gsm/libosmogsm.map | 1 |
2 files changed, 89 insertions, 0 deletions
diff --git a/src/gsm/gsm0480.c b/src/gsm/gsm0480.c index 5c73e5b8..dfd98773 100644 --- a/src/gsm/gsm0480.c +++ b/src/gsm/gsm0480.c @@ -33,6 +33,7 @@ #include <osmocom/gsm/protocol/gsm_04_80.h> #include <string.h> +#include <errno.h> static inline unsigned char *msgb_wrap_with_TL(struct msgb *msgb, uint8_t tag) { @@ -214,6 +215,93 @@ static int parse_ss_for_bs_req(const uint8_t *ss_req_data, uint16_t length, struct ss_request *req); +/*! Get pointer to the IE of a given type + * \param[in] hdr Pointer to the message starting from header + * \param[in] msg_len Length of the whole message + header + * \param[out] ie External pointer to be set + * \param[out] ie_len External IE length variable + * \param[in] ie_tag Tag value of the required IE + * \returns 0 in case of success, otherwise -ERRNO + * + * This function iterates over existing IEs within a given + * message (depending on its type), and looks for the one with + * given \ref ie_tag value. If the IE is found, the external + * pointer pointed by \ref ie will be set to its value part + * (omitting TL), and \ref ie_len will be set to the length. + * Otherwise, e.g. in case of parsing error, both \ref ie + * and \ref ie_len are set to NULL and 0 respectively. + */ +int gsm0480_extract_ie_by_tag(const struct gsm48_hdr *hdr, uint16_t msg_len, + uint8_t **ie, uint16_t *ie_len, uint8_t ie_tag) +{ + uint8_t pdisc, msg_type; + uint8_t *tlv, len; + + /* Init external variables */ + *ie_len = 0; + *ie = NULL; + + /* Drop incomplete / corrupted messages */ + if (msg_len < sizeof(*hdr)) + return -EINVAL; + + pdisc = gsm48_hdr_pdisc(hdr); + msg_type = gsm48_hdr_msg_type(hdr); + + /* Drop non-SS related messages */ + if (pdisc != GSM48_PDISC_NC_SS) + return -EINVAL; + + len = msg_len - sizeof(*hdr); + tlv = (uint8_t *) hdr->data; + + /* Parse a message depending on its type */ + switch (msg_type) { + /* See table 2.5: RELEASE COMPLETE message content */ + case GSM0480_MTYPE_RELEASE_COMPLETE: + /* See tables 2.3 and 2.4: REGISTER message content */ + case GSM0480_MTYPE_REGISTER: + /* Iterate over TLV-based IEs */ + while (len > 2) { + if (tlv[0] == ie_tag) { + *ie_len = tlv[1]; + *ie = tlv + 2; + return 0; + } + + len -= tlv[1] + 2; + tlv += tlv[1] + 2; + continue; + } + + /* The Facility IE is mandatory for REGISTER */ + if (msg_type == GSM0480_MTYPE_REGISTER) + if (ie_tag == GSM0480_IE_FACILITY) + return -EINVAL; + break; + + /* See table 2.2: FACILITY message content */ + case GSM0480_MTYPE_FACILITY: + /* There is no other IEs */ + if (ie_tag != GSM0480_IE_FACILITY) + break; + + /* Mandatory LV-based Facility IE */ + if (len < 2) + return -EINVAL; + + *ie_len = tlv[0]; + *ie = tlv + 1; + return 0; + + default: + /* Wrong message type, out of specs */ + return -EINVAL; + } + + return 0; +} + /* Decode a mobile-originated USSD-request message */ int gsm0480_decode_ussd_request(const struct gsm48_hdr *hdr, uint16_t len, struct ussd_request *req) diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map index 117cecfa..4aaed46e 100644 --- a/src/gsm/libosmogsm.map +++ b/src/gsm/libosmogsm.map @@ -89,6 +89,7 @@ gsm0480_create_unstructuredSS_Notify; gsm0480_create_ussd_resp; gsm0480_create_ussd_notify; gsm0480_create_ussd_release_complete; +gsm0480_extract_ie_by_tag; gsm0480_decode_ussd_request; gsm0480_decode_ss_request; gsm0480_wrap_facility; |