From: Hansong Zhang <hsz@google.com>
Date: Fri, 25 Sep 2020 02:57:01 +0000 (-0700)
Subject: Enforce remote MTU requirement in L2CAP directly
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=679dfc5152fa78182bc8b579faff9e0d8092a83c;p=android-x86%2Fsystem-bt.git

Enforce remote MTU requirement in L2CAP directly

AVCT_BR and BNEP don't need to enforce it locally.

Bug: 159815595
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: I090d4e31b76e0098fc77e707ebd2eacf4cd78b7b
---

diff --git a/stack/avct/avct_l2c_br.cc b/stack/avct/avct_l2c_br.cc
index 9bbaf5708..96fb81dab 100644
--- a/stack/avct/avct_l2c_br.cc
+++ b/stack/avct/avct_l2c_br.cc
@@ -287,21 +287,11 @@ void avct_l2c_br_config_ind_cback(uint16_t lcid, tL2CAP_CFG_INFO* p_cfg) {
 
   AVCT_TRACE_DEBUG("%s peer_mtu:%d use:%d", __func__, p_lcb->peer_mtu, max_mtu);
 
-  if (p_lcb->peer_mtu >= AVCT_MIN_BROWSE_MTU)
-    p_cfg->result = L2CAP_CFG_OK;
-  else {
-    p_cfg->result = L2CAP_CFG_UNACCEPTABLE_PARAMS;
-    p_cfg->mtu_present = true;
-    p_cfg->mtu = AVCT_MIN_BROWSE_MTU;
-  }
+  p_cfg->result = L2CAP_CFG_OK;
 
   /* send L2CAP configure response */
   L2CA_ConfigRsp(lcid, p_cfg);
 
-  if (p_cfg->result != L2CAP_CFG_OK) {
-    return;
-  }
-
   /* if first config ind */
   if ((p_lcb->ch_flags & AVCT_L2C_CFG_IND_DONE) == 0) {
     /* update flags */
diff --git a/stack/bnep/bnep_main.cc b/stack/bnep/bnep_main.cc
index 46287eab2..892fc888a 100644
--- a/stack/bnep/bnep_main.cc
+++ b/stack/bnep/bnep_main.cc
@@ -205,7 +205,6 @@ static void bnep_connect_cfm(uint16_t l2cap_cid, uint16_t result) {
  ******************************************************************************/
 static void bnep_config_ind(uint16_t l2cap_cid, tL2CAP_CFG_INFO* p_cfg) {
   tBNEP_CONN* p_bcb;
-  uint16_t result, mtu = 0;
 
   /* Find CCB based on CID */
   p_bcb = bnepu_find_bcb_by_cid(l2cap_cid);
@@ -217,29 +216,13 @@ static void bnep_config_ind(uint16_t l2cap_cid, tL2CAP_CFG_INFO* p_cfg) {
 
   BNEP_TRACE_EVENT("BNEP - Rcvd cfg ind, CID: 0x%x", l2cap_cid);
 
-  /* Remember the remote MTU size */
-  if ((!p_cfg->mtu_present) || (p_cfg->mtu < BNEP_MTU_SIZE)) {
-    mtu = p_cfg->mtu;
-    p_cfg->flush_to_present = false;
-    p_cfg->mtu_present = true;
-    p_cfg->mtu = BNEP_MTU_SIZE;
-    p_cfg->result = result = L2CAP_CFG_UNACCEPTABLE_PARAMS;
-  } else {
-
-    /* For now, always accept configuration from the other side */
-    p_cfg->flush_to_present = false;
-    p_cfg->mtu_present = false;
-    p_cfg->result = result = L2CAP_CFG_OK;
-  }
+  /* For now, always accept configuration from the other side */
+  p_cfg->flush_to_present = false;
+  p_cfg->mtu_present = false;
+  p_cfg->result = L2CAP_CFG_OK;
 
   L2CA_ConfigRsp(l2cap_cid, p_cfg);
 
-  if (result != L2CAP_CFG_OK) {
-    BNEP_TRACE_EVENT("BNEP - Rcvd cfg ind with bad MTU %d, CID: 0x%x", mtu,
-                     l2cap_cid);
-    return;
-  }
-
   p_bcb->con_flags |= BNEP_FLAGS_HIS_CFG_DONE;
 
   if (p_bcb->con_flags & BNEP_FLAGS_MY_CFG_DONE) {
diff --git a/stack/l2cap/l2c_utils.cc b/stack/l2cap/l2c_utils.cc
index 3d64cc6db..55626d1a5 100644
--- a/stack/l2cap/l2c_utils.cc
+++ b/stack/l2cap/l2c_utils.cc
@@ -1752,14 +1752,19 @@ uint8_t l2cu_process_peer_cfg_req(tL2C_CCB* p_ccb, tL2CAP_CFG_INFO* p_cfg) {
   bool flush_to_ok = true;
   bool fcr_ok = true;
   uint8_t fcr_status;
+  uint16_t required_remote_mtu =
+      std::max<uint16_t>(L2CAP_MIN_MTU, p_ccb->p_rcb->required_remote_mtu);
 
   /* Ignore FCR parameters for basic mode */
   if (!p_cfg->fcr_present) p_cfg->fcr.mode = L2CAP_FCR_BASIC_MODE;
 
-  /* Save the MTU that our peer can receive */
-  if (p_cfg->mtu_present) {
+  if (!p_cfg->mtu_present && required_remote_mtu > L2CAP_DEFAULT_MTU) {
+    // We reject if we have a MTU requirement higher than default MTU
+    p_cfg->mtu = required_remote_mtu;
+    mtu_ok = false;
+  } else if (p_cfg->mtu_present) {
     /* Make sure MTU is at least the minimum */
-    if (p_cfg->mtu >= L2CAP_MIN_MTU) {
+    if (p_cfg->mtu >= required_remote_mtu) {
       /* In basic mode, limit the MTU to our buffer size */
       if ((!p_cfg->fcr_present) && (p_cfg->mtu > L2CAP_MTU_SIZE))
         p_cfg->mtu = L2CAP_MTU_SIZE;
@@ -1769,7 +1774,7 @@ uint8_t l2cu_process_peer_cfg_req(tL2C_CCB* p_ccb, tL2CAP_CFG_INFO* p_cfg) {
       p_ccb->peer_cfg.mtu_present = true;
     } else /* Illegal MTU value */
     {
-      p_cfg->mtu = L2CAP_MIN_MTU;
+      p_cfg->mtu = required_remote_mtu;
       mtu_ok = false;
     }
   }