gsm: Implement the size checking of the hello packet

diff --git a/gsm.cpp b/gsm.cpp
index ee46ff6..a1ab7b0 100644 (file)
--- a/gsm.cpp
+++ b/gsm.cpp
@@ -1126,6 +1126,34 @@ static int mncc_fd_read(struct lcr_fd *lfd, void *inst, int idx)
                        mncc_fd_close(lcr_gsm, lfd);
                        return 0;
                }
+               if (hello->mncc_size != sizeof(struct gsm_mncc)) {
+                       PERROR("MNCC gsm_mncc size differs: %u %u\n",
+                               hello->mncc_size, sizeof(struct gsm_mncc));
+                       mncc_fd_close(lcr_gsm, lfd);
+                       return 0;
+               }
+               if (hello->data_frame_size != sizeof(struct gsm_data_frame)) {
+                       PERROR("MNCC gsm_mncc size differs: %u %u\n",
+                               hello->data_frame_size, sizeof(struct gsm_data_frame));
+                       mncc_fd_close(lcr_gsm, lfd);
+                       return 0;
+               }
+
+#define CHECK_OFFSET(hello, field, lcr_gsm, lfd)       \
+               if (hello->field ##_offset != __builtin_offsetof(struct gsm_mncc, field)) {     \
+                       PERROR("MNCC gsm_mncc offset of %s is %u %u\n",                         \
+                               #field, hello->field ##_offset,                                 \
+                               __builtin_offsetof(struct gsm_mncc, field));                    \
+                       mncc_fd_close(lcr_gsm, lfd);                                            \
+                       return 0;                                                               \
+               }
+
+               CHECK_OFFSET(hello, called, lcr_gsm, lfd);
+               CHECK_OFFSET(hello, signal, lcr_gsm, lfd);
+               CHECK_OFFSET(hello, emergency, lcr_gsm, lfd);
+               CHECK_OFFSET(hello, lchan_type, lcr_gsm, lfd);
+#undef CHECK_OFFSET
+
                break;
        }