Add function to find the device IP address

Parse the result of "adb shell ip route" to find the device IP address.

PR #2827 <https://github.com/Genymobile/scrcpy/pull/2827>

app/src/adb.c

@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "adb_parser.h"
 #include "util/file.h"
 #include "util/log.h"
 #include "util/process_intr.h"
@@ -389,3 +390,40 @@ adb_get_serialno(struct sc_intr *intr, unsigned flags) {
 
     return strdup(buf);
 }
+
+char *
+adb_get_device_ip(struct sc_intr *intr, const char *serial, unsigned flags) {
+    const char *const cmd[] = {"shell", "ip", "route"};
+
+    sc_pipe pout;
+    sc_pid pid = adb_execute_p(serial, cmd, ARRAY_LEN(cmd), flags, &pout);
+    if (pid == SC_PROCESS_NONE) {
+        LOGD("Could not execute \"ip route\"");
+        return NULL;
+    }
+
+    // "adb shell ip route" output should contain only a few lines
+    char buf[1024];
+    ssize_t r = sc_pipe_read_all_intr(intr, pid, pout, buf, sizeof(buf));
+    sc_pipe_close(pout);
+
+    bool ok = process_check_success_intr(intr, pid, "ip route", flags);
+    if (!ok) {
+        return NULL;
+    }
+
+    if (r == -1) {
+        return false;
+    }
+
+    assert((size_t) r <= sizeof(buf));
+    if (r == sizeof(buf) && buf[sizeof(buf) - 1] != '\0')  {
+        // The implementation assumes that the output of "ip route" fits in the
+        // buffer in a single pass
+        LOGW("Result of \"ip route\" does not fit in 1Kb. "
+             "Please report an issue.\n");
+        return NULL;
+    }
+
+    return sc_adb_parse_device_ip_from_output(buf, r);
+}

app/src/adb.h

@@ -66,4 +66,13 @@ adb_disconnect(struct sc_intr *intr, const char *ip_port, unsigned flags);
 char *
 adb_get_serialno(struct sc_intr *intr, unsigned flags);
 
+/**
+ * Attempt to retrieve the device IP
+ *
+ * Return the IP as a string of the form "xxx.xxx.xxx.xxx", to be freed by the
+ * caller, or NULL on error.
+ */
+char *
+adb_get_device_ip(struct sc_intr *intr, const char *serial, unsigned flags);
+
 #endif

app/src/adb_parser.c

@@ -0,0 +1,65 @@
+#include "adb_parser.h"
+
+#include <assert.h>
+#include <string.h>
+
+#include "util/log.h"
+#include "util/str.h"
+
+static char *
+sc_adb_parse_device_ip_from_line(char *line, size_t len) {
+    // One line from "ip route" looks lile:
+    // "192.168.1.0/24 dev wlan0  proto kernel  scope link  src 192.168.1.x"
+
+    // Get the location of the device name (index of "wlan0" in the example)
+    ssize_t idx_dev_name = sc_str_index_of_column(line, 2, " ");
+    if (idx_dev_name == -1) {
+        return NULL;
+    }
+
+    // Get the location of the ip address (column 8, but column 6 if we start
+    // from column 2). Must be computed before truncating individual columns.
+    ssize_t idx_ip = sc_str_index_of_column(&line[idx_dev_name], 6, " ");
+    if (idx_ip == -1) {
+        return NULL;
+    }
+    // idx_ip is searched from &line[idx_dev_name]
+    idx_ip += idx_dev_name;
+
+    char *dev_name = &line[idx_dev_name];
+    sc_str_truncate(dev_name, len - idx_dev_name + 1, " \t");
+
+    char *ip = &line[idx_ip];
+    sc_str_truncate(ip, len - idx_ip + 1, " \t");
+
+    // Only consider lines where the device name starts with "wlan"
+    if (strncmp(dev_name, "wlan", sizeof("wlan") - 1)) {
+        LOGD("Device ip lookup: ignoring %s (%s)", ip, dev_name);
+        return NULL;
+    }
+
+    return strdup(ip);
+}
+
+char *
+sc_adb_parse_device_ip_from_output(char *buf, size_t buf_len) {
+    size_t idx_line = 0;
+    while (idx_line < buf_len && buf[idx_line] != '\0') {
+        char *line = &buf[idx_line];
+        size_t len = sc_str_truncate(line, buf_len - idx_line, "\n");
+
+        // The same, but without any trailing '\r'
+        size_t line_len = sc_str_remove_trailing_cr(line, len);
+
+        char *ip = sc_adb_parse_device_ip_from_line(line, line_len);
+        if (ip) {
+            // Found
+            return ip;
+        }
+
+        // The next line starts after the '\n' (replaced by `\0`)
+        idx_line += len + 1;
+    }
+
+    return NULL;
+}

app/src/adb_parser.h

@@ -0,0 +1,14 @@
+#ifndef SC_ADB_PARSER_H
+#define SC_ADB_PARSER_H
+
+#include "common.h"
+
+#include "stddef.h"
+
+/**
+ * Parse the ip from the output of `adb shell ip route`
+ */
+char *
+sc_adb_parse_device_ip_from_output(char *buf, size_t buf_len);
+
+#endif