Minimal version of the LTE downgrade analyzer

This also renames the lte_parser crate to telcom_parser, since it'll
handle any 2G or 3G parsing going forward.

lib/src/analysis/lte_downgrade.rs

@@ -0,0 +1,83 @@
+use std::borrow::Cow;
+
+use super::analyzer::{Analyzer, Event, EventType, Severity};
+use super::information_element::{InformationElement, LteInformationElement};
+use telcom_parser::lte_rrc::{BCCH_DL_SCH_MessageType, BCCH_DL_SCH_MessageType_c1, CellReselectionPriority, SystemInformationBlockType7, SystemInformationCriticalExtensions, SystemInformation_r8_IEsSib_TypeAndInfo, SystemInformation_r8_IEsSib_TypeAndInfo_Entry};
+
+/// Based on heuristic T7 from Shinjo Park's "Why We Cannot Win".
+pub struct LteSib7DowngradeAnalyzer {
+}
+
+impl LteSib7DowngradeAnalyzer {
+    fn unpack_system_information<'a>(&self, ie: &'a InformationElement) -> Option<&'a SystemInformation_r8_IEsSib_TypeAndInfo> {
+        if let InformationElement::LTE(message) = ie {
+            if let LteInformationElement::BcchDlSch(bcch_dl_sch_message) = message {
+                if let BCCH_DL_SCH_MessageType::C1(BCCH_DL_SCH_MessageType_c1::SystemInformation(system_information)) = &bcch_dl_sch_message.message {
+                    if let SystemInformationCriticalExtensions::SystemInformation_r8(sib) = &system_information.critical_extensions {
+                        return Some(&sib.sib_type_and_info);
+                    }
+                }
+            }
+        }
+        None
+    }
+}
+
+// TODO: keep track of SIB state to compare LTE reselection blocks w/ 2g/3g ones
+impl Analyzer for LteSib7DowngradeAnalyzer {
+    fn get_name(&self) -> Cow<str> {
+        Cow::from("LTE SIB 7 Downgrade")
+    }
+
+    fn get_description(&self) -> Cow<str> {
+        Cow::from("Tests for LTE cells broadcasting a SIB type 7 which include 2G/3G frequencies with higher priorities.")
+    }
+
+    fn analyze_information_element(&mut self, ie: &InformationElement) -> Option<super::analyzer::Event> {
+        let sibs = &self.unpack_system_information(ie)?.0;
+        for sib in sibs {
+            match sib {
+                SystemInformation_r8_IEsSib_TypeAndInfo_Entry::Sib6(sib6) => {
+                    if let Some(carrier_info_list) = sib6.carrier_freq_list_utra_fdd.as_ref() {
+                        for carrier_info in &carrier_info_list.0 {
+                            if let Some(CellReselectionPriority(p)) = carrier_info.cell_reselection_priority {
+                                if p == 0 {
+                                    return Some(Event {
+                                        event_type: EventType::QualitativeWarning(Severity::High),
+                                        message: "LTE cell advertised a 3G cell for priority 0 reselection".to_string(),
+                                    });
+                                }
+                            }
+                        }
+                    }
+                    if let Some(carrier_info_list) = sib6.carrier_freq_list_utra_tdd.as_ref() {
+                        for carrier_info in &carrier_info_list.0 {
+                            if let Some(CellReselectionPriority(p)) = carrier_info.cell_reselection_priority {
+                                if p == 0 {
+                                    return Some(Event {
+                                        event_type: EventType::QualitativeWarning(Severity::High),
+                                        message: "LTE cell advertised a 3G cell for priority 0 reselection".to_string(),
+                                    });
+                                }
+                            }
+                        }
+                    }
+                },
+                SystemInformation_r8_IEsSib_TypeAndInfo_Entry::Sib7(SystemInformationBlockType7 { carrier_freqs_info_list: Some(carrier_info_list), .. }) => {
+                    for carrier_info in &carrier_info_list.0 {
+                        if let Some(CellReselectionPriority(p)) = carrier_info.common_info.cell_reselection_priority {
+                            if p == 0 {
+                                return Some(Event {
+                                    event_type: EventType::QualitativeWarning(Severity::High),
+                                    message: "LTE cell advertised a 2G cell for priority 0 reselection".to_string(),
+                                });
+                            }
+                        }
+                    }
+                },
+                _ => {},
+            }
+        }
+        None
+    }
+}