Kernel: Expose source information of incoming UDP packets

2 files changed, 57 insertions, 6 deletions

diff --git a/scalls/recvfrom.c b/scalls/recvfrom.c
index 0e37153..1770fa1 100644
--- a/scalls/recvfrom.c
+++ b/scalls/recvfrom.c
@@ -1,15 +1,59 @@
+#include <assert.h>
 #include <fs/vfs.h>
+#include <math.h>
 #include <poll.h>
 #include <scalls/recvfrom.h>
 
-size_t syscall_recvfrom(int socket, void *buffer, size_t length, int flags,
-                        struct sockaddr *address, socklen_t *address_len) {
+size_t syscall_recvfrom(
+    int socket, void *buffer, size_t length, int flags,
+    struct two_args
+        *extra_args /*struct sockaddr *address, socklen_t *address_len*/) {
+
+  struct sockaddr *address = (struct sockaddr *)extra_args->a;
+  socklen_t *address_len = (socklen_t *)extra_args->b;
+  kprintf("address: %x\n", address);
+  kprintf("address_len: %x\n", address_len);
+
   if (flags & MSG_WAITALL) {
     struct pollfd fds[1];
     fds[0].fd = socket;
     fds[0].events = POLLIN;
     poll(fds, 1, 0);
   }
-  kprintf("got event\n");
-  return vfs_pread(socket, buffer, length, 0);
+
+  uint16_t data_length;
+  socklen_t tmp_socklen;
+  vfs_pread(socket, &tmp_socklen, sizeof(socklen_t), 0);
+  if (address_len)
+    *address_len = tmp_socklen;
+  if (address) {
+    vfs_pread(socket, address, tmp_socklen, 0);
+  } else {
+    // We still have to throwaway the data.
+    char devnull[100];
+    for (; tmp_socklen;) {
+      int rc = vfs_pread(socket, devnull, min(tmp_socklen, 100), 0);
+      assert(rc >= 0);
+      tmp_socklen -= rc;
+    }
+  }
+
+  vfs_pread(socket, &data_length, sizeof(data_length), 0);
+  // If it is reading less than the packet length that could cause
+  // problems as the next read will not be put at a new header. Luckily
+  // it seems as if other UNIX systems can discard the rest of the
+  // packet if not read.
+
+  // Read in the data requested
+  int read_len = min(length, data_length);
+  int rc = vfs_pread(socket, buffer, read_len, 0);
+  // Discard the rest of the packet
+  int rest = data_length - read_len;
+  char devnull[100];
+  for (; rest;) {
+    int rc = vfs_pread(socket, devnull, 100, 0);
+    assert(rc >= 0);
+    rest -= rc;
+  }
+  return rc;
 }
diff --git a/scalls/recvfrom.h b/scalls/recvfrom.h
index 9897899..d81a1e0 100644
--- a/scalls/recvfrom.h
+++ b/scalls/recvfrom.h
@@ -1,4 +1,11 @@
 #include <socket.h>
 
-size_t syscall_recvfrom(int socket, void *buffer, size_t length, int flags,
-                         struct sockaddr *address, socklen_t *address_len);
+struct two_args {
+  uint32_t a;
+  uint32_t b;
+};
+
+size_t syscall_recvfrom(
+    int socket, void *buffer, size_t length, int flags,
+    struct two_args
+        *extra_args /*struct sockaddr *address, socklen_t *address_len*/);