initial commit

.clang-format

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+# Linux-like style
+BasedOnStyle: LLVM
+IndentWidth: 4
+UseTab: Never
+BreakBeforeBraces: Linux
+AllowShortIfStatementsOnASingleLine: true
+IndentCaseLabels: false
+# Force pointers to the type
+DerivePointerAlignment: false
+PointerAlignment: Left

.gitattributes

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+.gitattributes export-ignore
+.gitignore export-ignore

.gitignore

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+wakeup
+*.o
+*.exe

LICENSE.md

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+Copyright (C) 2020 Jan Wolff
+
+This software is provided 'as-is', without any express or implied warranty. In
+no event will the authors be held liable for any damages arising from the use
+of this software.  Permission is granted to anyone to use this software for any
+purpose, including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim
+   that you wrote the original software. If you use this software in a product,
+   an acknowledgment in the product documentation would be appreciated but is
+   not required.
+2. Altered source versions must be plainly marked as such, and must not be
+   misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.

Makefile

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+CC ?= gcc
+CFLAGS ?= -std=c99 -Wall -Werror
+OBJ = wakeup.o
+BIN = wakeup
+PREFIX ?= /usr
+
+prog: $(OBJ)
+	$(CC) $(CFLAGS) $(OBJ) -o $(BIN)
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c $<
+
+install: prog
+	mkdir -p ${PREFIX}/bin
+	install -m 755 -o root -g root -s ${BIN} ${PREFIX}/bin
+
+format:
+	clang-format -i *.c
+
+clean:
+	rm *.o
+	rm $(BIN)
+
+.PHONY: install format clean

README.md

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+Wakeup
+======
+
+Performs Wake On Lan by broadcasting a magic packet targeting the given MAC
+address.

wakeup.c

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+#include <arpa/inet.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void printUsage()
+{
+    puts("usage: wakeup <MAC> <BROADCAST> [PORT]");
+    puts("  MAC: interface address to wakeup (e.g. ff:ff:ff:ff:ff:ff)");
+    puts("  BROADCAST: broadcast address of subnet (e.g. 192.168.2.255)");
+    puts("  PORT: port to send UDP packet on (default: 7)");
+}
+
+/*
+Use the UDP broadcast method to send the magic wakeup packet.
+*/
+int bcast_wakeup(const char* macAddr, const char* broadcast, in_port_t port)
+{
+    int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+    if (sock < 1) {
+        perror("could not open socket");
+        exit(EXIT_FAILURE);
+    }
+
+    int opt_broadcast = 1;
+    setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &opt_broadcast,
+               sizeof(opt_broadcast));
+
+    struct in_addr ip;
+    if (!inet_aton(broadcast, &ip)) {
+        fputs("could not parse broadcast IP address", stderr);
+        exit(EXIT_FAILURE);
+    }
+
+    struct sockaddr_in socket_addr;
+    memset(&socket_addr, 0, sizeof(socket_addr));
+    socket_addr.sin_port = port;
+    socket_addr.sin_family = AF_INET;
+    socket_addr.sin_addr.s_addr = ip.s_addr;
+
+    uint8_t macValues[6];
+    if (sscanf(macAddr, "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx", &macValues[0],
+               &macValues[1], &macValues[2], &macValues[3], &macValues[4],
+               &macValues[5]) != 6) {
+        fputs("could not parse MAC address", stderr);
+        exit(EXIT_FAILURE);
+    }
+
+    uint8_t data[6 + 16 * 6];
+    memset(&data, 0xFF, 6); // sync stream for magic packet
+    for (size_t i = 0; i < 16;
+         i++) { // followed by 16 repititions of mac address
+        memcpy(data + 6 + 6 * i, &macValues, 6);
+    }
+
+    if (sendto(sock, data, sizeof(data), 0, (struct sockaddr*)&socket_addr,
+               sizeof(socket_addr)) < 0) {
+        fputs("packet sending failed", stderr);
+        perror("Error Code:");
+        exit(EXIT_FAILURE);
+    }
+    return 1;
+}
+
+int main(int argc, char* argv[])
+{
+    const char* mac;
+    const char* ip;
+    in_port_t port = 7;
+    if (argc < 3) {
+        printUsage();
+        exit(0);
+    } else {
+        mac = argv[1];
+        ip = argv[2];
+    }
+    if (argc > 3) {
+        port = atoi(argv[3]);
+    }
+    bcast_wakeup(mac, ip, port);
+    return 0;
+}