From ac0c70f74a5badbebec721c2be0602ea98c0437b Mon Sep 17 00:00:00 2001
From: Andrey Konovalov <andreyknvl@google.com>
Date: Thu, 27 Apr 2017 20:31:00 +0200
Subject: prog, executor: move checksum computation to executor

This commit moves checksum computation to executor. This will allow to embed
dynamically generated values (like TCP sequence numbers) into packets.
---
 csource/common.go  | 30 ++++++++++++++++++++++++++++++
 csource/csource.go | 27 ++++++++++++++++++++++++++-
 2 files changed, 56 insertions(+), 1 deletion(-)

(limited to 'csource')

diff --git a/csource/common.go b/csource/common.go
index f09cbf24d..2551cbbb9 100644
--- a/csource/common.go
+++ b/csource/common.go
@@ -275,6 +275,36 @@ static uintptr_t syz_emit_ethernet(uintptr_t a0, uintptr_t a1)
 }
 #endif
 
+struct csum_inet {
+	uint32_t acc;
+};
+
+void csum_inet_init(struct csum_inet* csum)
+{
+	csum->acc = 0;
+}
+
+void csum_inet_update(struct csum_inet* csum, const uint8_t* data, size_t length)
+{
+	if (length == 0)
+		return;
+
+	size_t i;
+	for (i = 0; i < length - 1; i += 2)
+		csum->acc += *(uint16_t*)&data[i];
+
+	if (length & 1)
+		csum->acc += (uint16_t)data[length - 1];
+
+	while (csum->acc > 0xffff)
+		csum->acc = (csum->acc & 0xffff) + (csum->acc >> 16);
+}
+
+uint16_t csum_inet_digest(struct csum_inet* csum)
+{
+	return ~csum->acc;
+}
+
 #ifdef __NR_syz_open_dev
 static uintptr_t syz_open_dev(uintptr_t a0, uintptr_t a1, uintptr_t a2)
 {
diff --git a/csource/csource.go b/csource/csource.go
index 1bf3fc7a1..6a21f54e6 100644
--- a/csource/csource.go
+++ b/csource/csource.go
@@ -226,8 +226,33 @@ loop:
 					esc = append(esc, '\\', 'x', hex(v>>4), hex(v<<4>>4))
 				}
 				fmt.Fprintf(w, "\tNONFAILING(memcpy((void*)0x%x, \"%s\", %v));\n", addr, esc, size)
+			case prog.ExecArgCsum:
+				csum_kind := read()
+				switch csum_kind {
+				case prog.ExecArgCsumInet:
+					fmt.Fprintf(w, "\tstruct csum_inet csum_%d;\n", n)
+					fmt.Fprintf(w, "\tcsum_inet_init(&csum_%d);\n", n)
+					csum_chunks_num := read()
+					for i := uintptr(0); i < csum_chunks_num; i++ {
+						chunk_kind := read()
+						chunk_value := read()
+						chunk_size := read()
+						switch chunk_kind {
+						case prog.ExecArgCsumChunkData:
+							fmt.Fprintf(w, "\tNONFAILING(csum_inet_update(&csum_%d, (const uint8_t*)0x%x, %d));\n", n, chunk_value, chunk_size)
+						case prog.ExecArgCsumChunkConst:
+							fmt.Fprintf(w, "\tuint%d_t csum_%d_chunk_%d = 0x%x;\n", chunk_size*8, n, i, chunk_value)
+							fmt.Fprintf(w, "\tcsum_inet_update(&csum_%d, (const uint8_t*)&csum_%d_chunk_%d, %d);\n", n, n, i, chunk_size)
+						default:
+							panic(fmt.Sprintf("unknown checksum chunk kind %v", chunk_kind))
+						}
+					}
+					fmt.Fprintf(w, "\tNONFAILING(*(uint16_t*)0x%x = csum_inet_digest(&csum_%d));\n", addr, n)
+				default:
+					panic(fmt.Sprintf("unknown csum kind %v", csum_kind))
+				}
 			default:
-				panic("bad argument type")
+				panic(fmt.Sprintf("bad argument type %v", instr))
 			}
 		case prog.ExecInstrCopyout:
 			addr := read()
-- 
cgit mrf-deployment